An open-source MCP (Model Context Protocol) server that gives AI assistants full access to Helm โ the Kubernetes package manager. Built with the native Helm Go SDK, supporting both Helm 3.x and 4.x in a single binary.
Use natural language to manage your Kubernetes deployments.
Connect helm-mcp to Claude, Cursor, VS Code, or any MCP-compatible client to install charts, manage releases, search repositories, and more โ all through conversation.
Table of Contents
Why helm-mcp?
- 46 MCP tools covering every Helm CLI command (minus shell completion and help)
- Dual Helm SDK support โ Helm v3 and v4 via native Go SDK (not CLI wrappers)
- Two transport modes โ stdio (default) and Streamable HTTP, stateless by default
- Cloud provider ready โ EKS, GKE, AKS kubeconfig formats work out of the box
- Security first โ Linux process hardening, credential memory zeroing, input validation, path traversal prevention
- Python wrapper โ FastMCP-based proxy that auto-discovers all tools
- Forward proxy support โ respects
HTTP_PROXY, HTTPS_PROXY, NO_PROXY
Installation
Pre-built Binaries
Download the latest release for your platform from GitHub Releases:
curl -LO https://github.com/SCGIS-Wales/helm-mcp/releases/latest/download/helm-mcp-darwin-arm64
chmod +x helm-mcp-darwin-arm64
sudo mv helm-mcp-darwin-arm64 /usr/local/bin/helm-mcp
curl -LO https://github.com/SCGIS-Wales/helm-mcp/releases/latest/download/helm-mcp-darwin-amd64
chmod +x helm-mcp-darwin-amd64
sudo mv helm-mcp-darwin-amd64 /usr/local/bin/helm-mcp
curl -LO https://github.com/SCGIS-Wales/helm-mcp/releases/latest/download/helm-mcp-linux-amd64
chmod +x helm-mcp-linux-amd64
sudo mv helm-mcp-linux-amd64 /usr/local/bin/helm-mcp
curl -LO https://github.com/SCGIS-Wales/helm-mcp/releases/latest/download/helm-mcp-linux-arm64
chmod +x helm-mcp-linux-arm64
sudo mv helm-mcp-linux-arm64 /usr/local/bin/helm-mcp
Build from Source
Requires Go 1.27+.
git clone https://github.com/SCGIS-Wales/helm-mcp.git
cd helm-mcp
make build
Docker
docker build -t helm-mcp .
docker run -v ~/.kube:/home/helmuser/.kube:ro helm-mcp --mode stdio
Python Package
See Python Package below for full details.
Quick Start
stdio mode (for Claude Code, Cursor, etc.)
HTTP mode (Streamable HTTP)
HTTP mode listens on 127.0.0.1:8080 by default. To accept remote clients,
configure authentication (see Authentication)
and bind explicitly, for example --addr 0.0.0.0:8080.
HTTP mode is stateless by default (MCP 2026-07-28): there is no
initialize handshake and no Mcp-Session-Id header, so the server can sit
behind a plain round-robin load balancer with no sticky sessions and no shared
session store. Clients speaking an older protocol revision still work โ the SDK
negotiates down automatically.
If a client needs the legacy per-session behaviour:
helm-mcp --mode http --stateless=false
Removed in v0.2.0: --mode sse. The HTTP+SSE transport has been
deprecated by the MCP specification since 2025-03-26 and is formally
Deprecated under the 2026-07-28 feature lifecycle policy. Use
--mode http, which serves Streamable HTTP on the same address.
MCP Client Configuration
Claude Desktop
Add to ~/.claude/claude_desktop_config.json:
{
"mcpServers": {
"helm": {
"command": "helm-mcp",
"args": ["--mode", "stdio"]
}
}
}
Claude Code
claude mcp add helm -- helm-mcp --mode stdio
Cursor / Windsurf / VS Code
Add to your MCP server configuration:
{
"helm-mcp": {
"command": "helm-mcp",
"args": ["--mode", "stdio"]
}
}
Remote / HTTP Clients
Start the server in HTTP mode, then connect any MCP-compatible client to the endpoint:
MCP Protocol Support
helm-mcp implements MCP 2026-07-28 and negotiates down to earlier
revisions (2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05) for older
clients, so upgrading the server does not require upgrading your client.
| Feature | Status |
|---|
| Tools | Supported โ 46 tools, with titles, annotations and output schemas |
| Stateless transport | Supported and the default for --mode http (--stateless=false to opt out) |
server/discover | Supported |
Deterministic tools/list order | Supported โ tools are returned sorted by name so clients and prompt caches keep hitting |
| Server instructions | Supported โ the server explains version selection, cluster targeting and destructive-tool safety |
| Resources / Prompts | Not applicable โ every Helm operation is a tool call |
| Tasks extension | Not implemented. Attractive for long helm install --wait runs, but client support is still thin. Tracked as a follow-up. |
| MRTR / Elicitation | Not implemented, deliberately. Helm tools take all their input as arguments, so there is no mid-call question to ask. |
| Roots / Sampling / Logging | Not implemented. All three are deprecated as of 2026-07-28 (SEP-2577). |
| HTTP+SSE transport | Removed in v0.2.0 โ deprecated by the specification. Use --mode http. |
Release Management (14)
| Tool | Description |
|---|
helm_install | Install a Helm chart as a new release |
helm_upgrade | Upgrade a release to a new chart version or values |
helm_uninstall | Uninstall a release and remove associated resources |
helm_rollback | Rollback a release to a previous revision |
helm_list | List releases (supports filters, sorting, pagination) |
helm_status | Display release status, revision, chart, and values |
helm_history | Show revision history of a release |
helm_test | Run the test suite for a release |
helm_get_all | Get all info (values, manifest, hooks, notes) for a release |
helm_get_hooks | Get hooks for a release |
helm_get_manifest | Get the Kubernetes manifest for a release |
helm_get_metadata | Get metadata for a release |
helm_get_notes | Get notes for a release |
helm_get_values | Get values for a release (user-supplied or computed) |
Chart Management (14)
| Tool | Description |
|---|
helm_create | Create a new chart with the given name |
helm_lint | Lint a chart for issues and best practices |
helm_template | Render templates locally without installing |
helm_package | Package a chart directory into an archive (.tgz) |
helm_pull | Download a chart from a repository or OCI registry |
helm_push | Push a chart archive to an OCI registry |
helm_verify | Verify a chart has a valid provenance file |
helm_show_all | Show all chart info (Chart.yaml, values, README, CRDs) |
helm_show_chart | Show Chart.yaml of a chart |
helm_show_crds | Show CRDs of a chart |
helm_show_readme | Show README of a chart |
helm_show_values | Show default values of a chart |
helm_dependency_build | Build charts/ directory from Chart.lock |
helm_dependency_list | List dependencies for a chart |
Repository Management (5)
| Tool | Description |
|---|
helm_repo_add | Add a chart repository |
helm_repo_list | List configured chart repositories |
helm_repo_update | Update chart repository indexes |
helm_repo_remove | Remove chart repositories |
helm_repo_index | Generate an index file for chart archives |
Registry / OCI (2)
| Tool | Description |
|---|
helm_registry_login | Login to an OCI registry |
helm_registry_logout | Logout from an OCI registry |
Search (2)
| Tool | Description |
|---|
helm_search_hub | Search Artifact Hub for charts |
helm_search_repo | Search locally configured repositories |
Plugin Management (6)
| Tool | Description |
|---|
helm_plugin_install | Install a Helm plugin |
helm_plugin_list | List installed plugins |
helm_plugin_uninstall | Uninstall a plugin |
helm_plugin_update | Update a plugin |
helm_plugin_package | Package a plugin directory into a signed archive (v4 only) |
helm_plugin_verify | Verify a packaged plugin's signature and provenance (v4 only) |
Environment (2)
| Tool | Description |
|---|
helm_env | Print Helm environment information |
helm_version | Print Helm SDK version information |
Dependency Update (1)
| Tool | Description |
|---|
helm_dependency_update | Update charts/ based on Chart.yaml |
Every tool carries MCP annotations so a client โ or an agent deciding what to
call โ can tell a read at a glance from a change to your cluster.
| Annotation | Meaning | Tools |
|---|
readOnlyHint: true | Only reads state; safe to call freely | helm_list, helm_status, helm_history, all helm_get_*, all helm_show_*, helm_repo_list, helm_plugin_list, helm_dependency_list, helm_env, helm_version, helm_lint, helm_template, helm_verify, helm_plugin_verify, helm_search_* |
destructiveHint: true | Can remove or replace live state โ call only on explicit user intent | helm_uninstall, helm_rollback, helm_upgrade, helm_repo_remove, helm_plugin_uninstall |
openWorldHint: true | Reaches beyond the configured cluster (Artifact Hub, OCI registries, chart repos) | helm_search_hub, helm_search_repo, helm_pull, helm_push, all helm_show_*, helm_template, helm_registry_* |
idempotentHint: true | Repeating the call with the same arguments has no additional effect | all read-only tools, plus helm_repo_add, helm_repo_update, helm_dependency_*, helm_plugin_update |
Everything not listed as destructive is annotated destructiveHint: false,
which matters because the MCP specification defaults that hint to true.
Annotations are hints, not a security boundary โ a client may ignore them. For
a real boundary, use the OIDC scopes and roles described under
Security.
Structured Output
Eleven tools publish an outputSchema and return structuredContent alongside
the human-readable text, so clients can consume results without parsing prose:
helm_list, helm_status, helm_history, helm_get_metadata,
helm_get_values, helm_repo_list, helm_search_repo, helm_search_hub,
helm_plugin_list, helm_env, helm_version.
{
"releases": [
{ "name": "my-app", "namespace": "default", "revision": 3, "status": "deployed", ... }
],
"count": 1
}
The existing JSON text content is unchanged, so clients that parse it keep
working. Collections are wrapped in an object with a count rather than
returned as a bare array. Tools whose output is free-form YAML or text โ
helm_template, helm_lint, helm_get_manifest, helm_show_*,
helm_package, helm_dependency_list โ have no output schema, because there
is no useful shape to declare.
Helm CLI Coverage
Complete mapping of every helm CLI command to its helm-mcp MCP tool equivalent.
| Helm Command | MCP Tool | Status |
|---|
helm create | helm_create | Covered |
helm dependency build | helm_dependency_build | Covered |
helm dependency list | helm_dependency_list | Covered |
helm dependency update | helm_dependency_update | Covered |
helm env | helm_env | Covered |
helm get all | helm_get_all | Covered |
helm get hooks | helm_get_hooks | Covered |
helm get manifest | helm_get_manifest | Covered |
helm get metadata | helm_get_metadata | Covered |
helm get notes | helm_get_notes | Covered |
helm get values | helm_get_values | Covered |
helm history | helm_history | Covered |
helm install | helm_install | Covered |
helm lint | helm_lint | Covered |
helm list | helm_list | Covered |
helm package | helm_package | Covered |
helm plugin install | helm_plugin_install | Covered |
helm plugin list | helm_plugin_list | Covered |
helm plugin uninstall | helm_plugin_uninstall | Covered |
helm plugin package | helm_plugin_package | Covered (v4 only) |
helm plugin update | helm_plugin_update | Covered |
helm plugin verify | helm_plugin_verify | Covered (v4 only) |
helm pull | helm_pull | Covered |
helm push | helm_push | Covered |
helm registry login | helm_registry_login | Covered |
helm registry logout | helm_registry_logout | Covered |
helm repo add | helm_repo_add | Covered |
helm repo index | helm_repo_index | Covered |
helm repo list | helm_repo_list | Covered |
helm repo remove | helm_repo_remove | Covered |
helm repo update | helm_repo_update | Covered |
helm rollback | helm_rollback | Covered |
helm search hub | helm_search_hub | Covered |
helm search repo | helm_search_repo | Covered |
helm show all | helm_show_all | Covered |
helm show chart | helm_show_chart | Covered |
helm show crds | helm_show_crds | Covered |
helm show readme | helm_show_readme | Covered |
helm show values | helm_show_values | Covered |
helm status | helm_status | Covered |
helm template | helm_template | Covered |
helm test | helm_test | Covered |
helm uninstall | helm_uninstall | Covered |
helm upgrade | helm_upgrade | Covered |
helm verify | helm_verify | Covered |
helm version | helm_version | Covered |
helm completion | โ | Not applicable (shell utility) |
helm help | โ | Not applicable (shell utility) |
46 of 46 operational Helm commands are covered. The only excluded commands (completion, help) are shell utilities that have no meaning in an MCP context.
helm plugin package and helm plugin verify were introduced in Helm v4 alongside signed plugin distribution, so they require helm_version: "v4".
Kubernetes Authentication
Every tool accepts these authentication fields via the GlobalInput:
| Field | JSON Key | Description |
|---|
| Kubeconfig | kubeconfig | Path to kubeconfig file (defaults to $KUBECONFIG or ~/.kube/config) |
| Context | kube_context | Kubernetes context name to use |
| API Server | kube_apiserver | Override the API server URL from kubeconfig |
| Bearer Token | kube_token | Bearer token for API authentication |
| TLS Server Name | kube_tls_server_name | Server name for TLS certificate validation |
| Insecure TLS | kube_insecure_tls | Skip TLS certificate verification |
| Namespace | namespace | Target Kubernetes namespace |
EKS (AWS)
EKS uses exec-based authentication in kubeconfig. The standard kubeconfig generated by aws eks update-kubeconfig works out of the box:
{
"kubeconfig": "/home/user/.kube/config",
"kube_context": "arn:aws:eks:us-east-1:123456789:cluster/my-cluster"
}
Or with direct token authentication:
{
"kube_apiserver": "https://ABCDEF.gr7.us-east-1.eks.amazonaws.com",
"kube_token": "<bearer-token-from-aws-eks-get-token>"
}
GKE (Google Cloud)
GKE kubeconfig generated by gcloud container clusters get-credentials works out of the box:
{
"kubeconfig": "/home/user/.kube/config",
"kube_context": "gke_my-project_us-central1_my-cluster"
}
AKS (Azure)
AKS kubeconfig generated by az aks get-credentials works out of the box:
{
"kubeconfig": "/home/user/.kube/config",
"kube_context": "my-aks-cluster"
}
Helm Version Selection
Every tool supports a helm_version field to select between Helm v3 and v4:
{
"helm_version": "v4",
"release_name": "my-release"
}
"v4" (default) โ Uses Helm v4 SDK with Server-Side Apply, WASM plugins, label selectors
"v3" โ Uses Helm v3 SDK for backward compatibility
v4-Only Features
These fields are only available when using helm_version: "v4". Passing one
with "v3" is an error rather than a silent no-op.
server_side_apply โ Use Kubernetes server-side apply
take_ownership โ Skip Helm annotation checks
hide_secret โ Hide secrets in dry-run output
force_conflicts โ Force conflict resolution
selector โ Label selector for list operations
show_resources โ Show resources table in status
reset_then_reuse_values โ Reset then reuse values in upgrade
wait_strategy โ See below
Two tools are v4-only in their entirety: helm_plugin_package and
helm_plugin_verify.
Waiting: wait and wait_strategy
Helm v4 replaced v3's boolean --wait with a strategy enum, so
helm_install, helm_upgrade, helm_rollback and helm_uninstall accept a
wait_strategy field alongside wait:
wait_strategy | Behaviour |
|---|
"watcher" | Wait using kstatus โ what helm --wait does in v4 |
"legacy" | Wait using the v3 readiness checks |
"hookOnly" | Only wait for hooks; the CLI default when --wait is omitted |
wait_strategy takes precedence when set. Otherwise wait: true maps to
"watcher" and wait: false maps to "hookOnly".
Before v0.2.0 the v4 engine hardcoded the watcher strategy, so wait: false
was silently ignored and every v4 operation waited. If you relied on that
behaviour, set wait: true (or wait_strategy: "watcher") explicitly.
Available on both v3 and v4
rollback_on_failure (Helm's --atomic) is supported by both engines, and is
available on helm_install and helm_upgrade. So are devel, sub_notes,
hide_notes, skip_schema_validation, disable_openapi_validation and
enable_dns; output_dir and use_release_name on helm_install;
ignore_not_found and description on helm_uninstall; and all,
uninstalling and time_format on helm_list.
Python Package
A Python wrapper is available that uses FastMCP to create a transparent proxy around the helm-mcp Go binary. New tools added to the Go binary are automatically available in Python without code changes.
Installation
Requires Python 3.12+. The Go binary is bundled inside platform-specific wheels โ no Go toolchain is required. Supported platforms: linux-amd64, linux-arm64, darwin-amd64, darwin-arm64, windows-amd64. The binary is extracted from the wheel on first use, with SHA256 checksum verification to protect against tampering.
You can verify the binary is available:
Usage as a Server
from helm_mcp import create_server
server = create_server()
server.run()
server = create_server()
server.run(transport="http", host="127.0.0.1", port=8080)
Usage as a Client
import asyncio
from helm_mcp import create_client
async def main():
async with create_client() as client:
tools = await client.list_tools()
print(f"Available tools: {len(tools)}")
result = await client.call_tool("helm_list", {"namespace": "default"})
print(result)
result = await client.call_tool("helm_install", {
"release_name": "my-app",
"chart": "bitnami/nginx",
"namespace": "default",
})
print(result)
asyncio.run(main())
CLI
helm-mcp-python
helm-mcp-python --transport http --port 8080
helm-mcp-python --transport http --host 0.0.0.0 --allow-remote
helm-mcp-python --binary /usr/local/bin/helm-mcp
Integrating with FastMCP
The Python package is built on FastMCP and returns standard FastMCP server/client objects. You can compose it with other FastMCP servers:
from fastmcp import FastMCP
from helm_mcp import create_server as create_helm_server
app = FastMCP("my-platform")
helm = create_helm_server()
app.mount("helm", helm)
@app.tool()
def my_custom_tool(param: str) -> str:
return f"Custom: {param}"
app.run()
Binary Discovery
The Python package locates the helm-mcp Go binary in this order:
HELM_MCP_BINARY environment variable
- Bundled binary in the package
bin/ directory
- Auto-download from GitHub Releases (with SHA256 checksum verification)
helm-mcp on PATH
Environment Variables
The proxy forwards these environment variables to the Go subprocess:
| Category | Variables |
|---|
| Proxy | HTTP_PROXY, HTTPS_PROXY, NO_PROXY (and lowercase variants) |
| Kubernetes | KUBECONFIG, KUBERNETES_SERVICE_HOST, KUBERNETES_SERVICE_PORT |
| Helm | HELM_CACHE_HOME, HELM_CONFIG_HOME, HELM_DATA_HOME, HELM_PLUGINS, HELM_DEBUG |
| AWS | AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN, AWS_REGION, AWS_PROFILE |
| GCP | GOOGLE_APPLICATION_CREDENTIALS, CLOUDSDK_COMPUTE_ZONE |
| Azure | AZURE_TENANT_ID, AZURE_CLIENT_ID, AZURE_CLIENT_SECRET, AZURE_SUBSCRIPTION_ID |
| TLS | SSL_CERT_FILE, SSL_CERT_DIR |
Resilience Configuration (Python)
The Python package includes a comprehensive resilience stack built on FastMCP middleware, circuitbreaker, and tenacity. All settings are configurable via HELM_MCP_* environment variables with sensible defaults.
Environment Variables
| Variable | Type | Default | Description |
|---|
HELM_MCP_RETRY_ENABLED | bool | true | Enable proxy-level retry middleware |
HELM_MCP_RETRY_MAX_RETRIES | int | 2 | Maximum retry attempts |
HELM_MCP_RETRY_BASE_DELAY | float | 1.0 | Initial backoff delay (seconds) |
HELM_MCP_RETRY_MAX_DELAY | float | 30.0 | Maximum backoff delay (seconds) |
HELM_MCP_RETRY_BACKOFF_MULTIPLIER | float | 2.0 | Backoff multiplier |
HELM_MCP_RATE_LIMIT_ENABLED | bool | false | Enable token-bucket rate limiting |
HELM_MCP_RATE_LIMIT_MAX_RPS | float | 10.0 | Maximum requests per second |
HELM_MCP_RATE_LIMIT_BURST | int | 20 | Burst capacity |
HELM_MCP_CACHE_ENABLED | bool | false | Enable TTL-based response caching |
HELM_MCP_CACHE_TOOL_TTL | int | 300 | Tool call cache TTL (seconds) |
HELM_MCP_CACHE_LIST_TTL | int | 60 | Tool list cache TTL (seconds) |
HELM_MCP_ERROR_HANDLING_ENABLED | bool | true | Enable structured error responses |
HELM_MCP_ERROR_INCLUDE_TRACEBACK | bool | false | Include tracebacks in errors |
HELM_MCP_TIMING_ENABLED | bool | true | Enable request timing |
HELM_MCP_TIMING_DETAILED | bool | false | Use detailed timing middleware |
HELM_MCP_CIRCUIT_BREAKER_ENABLED | bool | true | Enable circuit breaker on tool calls |
HELM_MCP_CIRCUIT_BREAKER_FAILURE_THRESHOLD | int | 5 | Failures before circuit opens |
HELM_MCP_CIRCUIT_BREAKER_RESET_TIMEOUT | float | 30.0 | Seconds before half-open retry |
HELM_MCP_TENACITY_ENABLED | bool | true | Enable tenacity retry with jitter |
HELM_MCP_TENACITY_MAX_ATTEMPTS | int | 3 | Maximum retry attempts |
HELM_MCP_TENACITY_MIN_WAIT | float | 0.5 | Minimum wait between retries (seconds) |
HELM_MCP_TENACITY_MAX_WAIT | float | 10.0 | Maximum wait between retries (seconds) |
HELM_MCP_TENACITY_MULTIPLIER | float | 1.5 | Exponential backoff base |
HELM_MCP_BULKHEAD_ENABLED | bool | true | Enable concurrency limiter |
HELM_MCP_BULKHEAD_MAX_CONCURRENT | int | 10 | Maximum concurrent tool calls |
HELM_MCP_OTEL_ENABLED | bool | false | Enable OpenTelemetry tracing |
HELM_MCP_OTEL_SERVICE_NAME | str | helm-mcp | OTel service name |
HELM_MCP_OTEL_EXPORTER | str | console | OTel exporter (console or otlp) |
CLI Flags
helm-mcp-python --no-retry
helm-mcp-python --rate-limit 50
helm-mcp-python --cache
helm-mcp-python --no-circuit-breaker
helm-mcp-python --bulkhead-max 5
helm-mcp-python --otel
Programmatic Configuration
from helm_mcp import create_server, HelmClient
from helm_mcp.resilience import (
ResilienceConfig,
RateLimitConfig,
CircuitBreakerConfig,
BulkheadConfig,
)
config = ResilienceConfig(
rate_limit=RateLimitConfig(enabled=True, max_requests_per_second=50),
circuit_breaker=CircuitBreakerConfig(failure_threshold=3),
bulkhead=BulkheadConfig(max_concurrent=20),
)
server = create_server(resilience=config)
async with HelmClient(resilience=config) as helm:
releases = await helm.list(namespace="default")
OpenTelemetry
FastMCP emits traces via the OpenTelemetry API. To receive actual trace data, install the SDK:
pip install helm-mcp[otel]
Then enable tracing:
export HELM_MCP_OTEL_ENABLED=true
export HELM_MCP_OTEL_EXPORTER=otlp
export HELM_MCP_OTEL_SERVICE_NAME=helm-mcp
Response Payload Management
Large Helm outputs (manifests, values, template renders) can overflow LLM context windows. helm-mcp includes two layers of response size management to prevent this.
Response Truncation
All tool responses are automatically truncated when they exceed a configurable size limit. The default is 256 KB (~64K tokens). Truncated responses include metadata indicating the original size and a suggestion to use more specific queries.
Configure the limit via CLI flag or environment variable:
helm-mcp --mode stdio --max-response-bytes 524288
export HELM_MCP_MAX_RESPONSE_BYTES=524288
helm-mcp --mode stdio
The CLI flag takes precedence over the environment variable.
Manifest Sanitisation
Tools that return Kubernetes YAML (helm_get_manifest, helm_get_all, helm_get_hooks, helm_template) automatically strip noisy fields before returning results. This typically reduces manifest sizes by 40-60% without losing meaningful information.
Fields stripped:
metadata.managedFields โ internal Kubernetes bookkeeping (often the largest single field)
kubectl.kubernetes.io/last-applied-configuration โ redundant copy of the entire object
deployment.kubernetes.io/revision โ internal controller annotation
control-plane.alpha.kubernetes.io/leader โ leader election data
This sanitisation is always active and cannot be disabled, as these fields are never useful for LLM interactions. The original unsanitised data remains available through direct kubectl access.
Resilience Primitives
The internal/resilience package provides additional production resilience patterns:
| Pattern | Description |
|---|
| Circuit breaker | Three-state (Closed/Open/HalfOpen) pattern to fail fast when backends are unavailable. Configurable failure threshold and recovery timeout. |
| Retry with backoff | Exponential backoff with jitter for transient failures. Context-aware cancellation and retryable error filtering. |
| Per-tool timeouts | Category-based default timeouts: query (30s), mutate (120s), chart (60s), repo (60s). Respects existing context deadlines. |
Known Limitations
Plugin Verification Required (Helm v4 CLI)
All six plugin tools shell out to the system helm CLI, which is the only part
of helm-mcp that does not go through the Helm Go SDK โ Helm's plugin packages
are internal and not importable. Helm v4 requires plugin source verification by
default, and plugins that do not support it (like helm-diff) need
--verify=false, which the MCP tools do not yet expose.
- Workaround: install those plugins directly via
helm plugin install <url> --verify=false
- The published container image ships a pinned
helm CLI, so plugin tools work
there. If you run the binary directly, helm must be on PATH.
Security
Process Hardening (Linux)
When running on Linux, helm-mcp applies process-level hardening at startup to reduce the attack surface of the stdio transport. MCP servers running as IDE child processes inherit full user privileges โ these mitigations limit what an attacker can do if the process is compromised.
| Mechanism | What It Does |
|---|
| PR_SET_DUMPABLE(0) | Blocks ptrace attach, core dumps, and /proc/pid/mem reads. Prevents other processes from inspecting credentials in memory. |
| Capability dropping | Drops all Linux capabilities from the bounding set. No-op for non-root users (the common case), but protects against privilege escalation when running in misconfigured Docker/Kubernetes environments. |
| Credential memory zeroing | ZeroCredentials() is called via defer after every tool handler completes, overwriting bearer tokens and passwords in memory. This is defense-in-depth โ Go strings are immutable and the GC may retain copies, but it reduces the credential lifetime in our code paths. |
Hardening is best-effort and non-fatal โ failures are logged (with --debug) but never crash the process. On non-Linux platforms (macOS, Windows), hardening is skipped with an informational log message.
helm-mcp --mode stdio --debug 2>&1 | grep "security hardening"
helm-mcp --mode stdio --no-harden
Mechanisms Evaluated but Not Implemented
| Mechanism | Why Skipped |
|---|
| Seccomp BPF | The server uses exec.CommandContext for plugins and network I/O for Kubernetes API and registries. The syscall surface is too wide to filter safely without breaking Helm SDK internals across kernel versions. |
| Namespace isolation | The process needs access to ~/.kube/config, cloud credential files, DNS, and network. Namespace isolation would break core functionality. |
| Cgroup resource limits | A 5-minute pluginExecTimeout already bounds runaway operations, and the IDE manages process lifecycle. |
| AppArmor/SELinux profiles | High maintenance burden for dynamic file paths. Better deployed as an external artifact, not embedded in the binary. |
Credential Scrubbing
All error messages are automatically scrubbed to remove:
- Bearer tokens (including EKS, GKE, and Azure JWT tokens)
- Basic authentication credentials
- URL-embedded passwords (
https://user:password@host)
Every tool handler calls ValidateGlobalInput before executing, ensuring namespace and kubeconfig fields are validated on every request.
The security package provides validators for:
- Release names (DNS-1123 compliant)
- Namespace names
- Kubeconfig file paths (path traversal prevention, symlink detection, sensitive path rejection โ
/etc/shadow, /proc/, /dev/, /sys/ are blocked)
- URLs (scheme validation + SSRF protection: DNS resolution with private IP blocking for
0.0.0.0/8, 127.0.0.0/8, 10.0.0.0/8, 100.64.0.0/10, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16, IPv4-mapped addresses, NAT64, and IPv6 unspecified/loopback/link-local/unique-local ranges). Applied to repository URLs, URL chart references, remote values files, and OCI push targets
- File paths (traversal prevention, symlink rejection including symlinked parent directories, sensitive path rejection). Applied to values files, keyrings, CA/cert/key files, passphrase files, and output directories
- Repository names (alphanumeric, dots, dashes, underscores; prevents cache path traversal)
- Timeout durations (max 24h)
- Plugin names (alphanumeric + dashes/underscores, no leading dash to prevent argument injection)
File Permissions
- Repository configuration files are written with
0600 (owner read/write only)
- Config directories are created with
0700 (owner only)
HTTP Server Hardening
When running in HTTP mode:
- Listens on
127.0.0.1:8080 unless --addr says otherwise
ReadHeaderTimeout: 10s and ReadTimeout: 30s โ prevent slow client attacks
WriteTimeout: 30m (--write-timeout) โ long enough for helm_install/helm_upgrade with wait; raise it if clients use longer Helm timeouts
IdleTimeout: 120s โ reclaims idle connections
MaxHeaderBytes: 1MB โ prevents header-based DoS
- Graceful shutdown with 5-second timeout
Authentication (OIDC/OAuth2)
When running in HTTP mode, helm-mcp supports OAuth2/OIDC authentication with JWT validation, claims-based authorization, and structured audit logging. This aligns with the MCP Security Best Practices.
Authentication is fully opt-in. When no OIDC or token environment variables are set, the server runs without authentication (same as previous versions). Stdio mode is never affected by authentication configuration.
Quick Start โ Entra ID (Azure AD / ADFS)
export HELM_MCP_OIDC_ISSUER="https://login.microsoftonline.com/{tenant-id}/v2.0"
export HELM_MCP_OIDC_AUDIENCE="api://helm-mcp-server"
export HELM_MCP_REQUIRED_SCOPES="helm.read,helm.write"
export HELM_MCP_REQUIRED_ROLES="HelmOperator"
export HELM_MCP_ALLOWED_CLIENTS="client-app-id-1,client-app-id-2"
export HELM_MCP_OIDC_JWKS_URL="https://login.microsoftonline.com/{tenant-id}/discovery/v2.0/keys"
helm-mcp --mode http --addr 0.0.0.0:8080
Authentication events (auth_success, auth_failure) are written to stderr as JSON at Info level, independent of --debug.
Environment Variables
| Variable | Required | Description |
|---|
HELM_MCP_OIDC_ISSUER | Yes (for OIDC) | OIDC issuer URL. Token iss claim must match. |
HELM_MCP_OIDC_AUDIENCE | Yes (for OIDC) | Expected aud claim. Tokens issued for other resources are rejected. |
HELM_MCP_OIDC_JWKS_URL | No | JWKS endpoint for signature verification. Auto-discovered from issuer if omitted. |
HELM_MCP_REQUIRED_SCOPES | No | Comma-separated OAuth2 scopes required in the scp claim. |
HELM_MCP_REQUIRED_ROLES | No | Comma-separated app roles required in the roles claim. |
HELM_MCP_ALLOWED_CLIENTS | No | Comma-separated client app IDs allowed in azp/appid claim. |
HELM_MCP_SESSION_TTL | No | Session cache inactivity TTL (Go duration, e.g., 5m, 15m). Default: 5m. |
HELM_MCP_AUTH_TOKEN | No | Static bearer token (legacy). Lower priority than OIDC. |
Authentication Priority
- OIDC/OAuth2 โ if
HELM_MCP_OIDC_ISSUER is set, JWT validation with JWKS is enabled.
- Static bearer token โ if only
HELM_MCP_AUTH_TOKEN is set, constant-time comparison is used.
- No auth โ if neither is set, the server accepts all requests (suitable for local stdio usage).
Token Validation
Every incoming JWT is validated for:
| Check | Description |
|---|
| Signature | RSA signature verified against JWKS public keys (RS256/384/512). Keys are cached for 1 hour with automatic refresh on kid miss (key rotation). |
Issuer (iss) | Must exactly match HELM_MCP_OIDC_ISSUER. |
Audience (aud) | Must match HELM_MCP_OIDC_AUDIENCE. Tokens issued for other APIs are rejected โ this is the core defense against token passthrough. |
Expiry (exp) | Required. Expired tokens are rejected. |
Authorized Party (azp/appid) | Checked against HELM_MCP_ALLOWED_CLIENTS if configured. Supports both OIDC azp and Entra ID v1 appid claims. |
Scopes (scp) | Space-separated scopes checked against HELM_MCP_REQUIRED_SCOPES. |
Roles (roles) | Array of app roles checked against HELM_MCP_REQUIRED_ROLES. |
Session Cache
Validated tokens are cached in-memory to avoid redundant JWKS lookups:
- Inactivity TTL: 5 minutes by default (configurable via
HELM_MCP_SESSION_TTL, e.g., 5m, 10m, 1h)
- Token expiry: Cached tokens are never used beyond their
exp claim
- Cache key: SHA-256 hash of the raw bearer token (prevents raw token storage in memory)
- Sliding window: Each access resets the inactivity timer
- Maximum entries: 10,000 (oldest evicted on overflow)
Audit Logging
When OIDC authentication is enabled, structured audit events are emitted via slog for every authentication attempt:
level=INFO msg=security_audit audit.event_type=auth_success audit.principal_id=oid-123 audit.principal_name=user@example.com audit.tenant_id=tenant-abc audit.client_app_id=client-1 audit.scopes="helm.read helm.write" audit.token_id=uti-xyz audit.remote_addr=10.0.0.1:54321
Audit events include: principal ID/name, tenant ID, client app ID, scopes, roles, token ID, session ID, action, resource, result, duration, and remote address. Enable --debug for full audit visibility, or configure your log aggregator to capture security_audit messages.
On-Behalf-Of (OBO) Token Exchange
When helm-mcp needs to call a downstream API (such as the Kubernetes API) on behalf of the authenticated user, it exchanges the incoming token for a new one scoped to that downstream service. This avoids forwarding the original token, which could be misused if the downstream service is compromised or if the token's audience doesn't match.
How It Works
User MCP Client helm-mcp (MCP Server) Kubernetes API
โ โ โ โ
โโ(SSO)โโโโโโโถโ gets token โ โ
โ โ aud=helm-mcp โ โ
โ โโ(Bearer token)โโโโโโโถโ โ
โ โ โโOBO exchangeโโโโโโโโโโโถโ
โ โ โ grant_type=jwt-bearer โ
โ โ โ assertion=user token โ
โ โ โ scope=K8s API scopes โ
โ โ โโโnew tokenโโโโโโโโโโโโโโโ
โ โ โ aud=Kubernetes API โ
โ โ โโ(K8s API call)โโโโโโโโโถโ
โ โ โ with OBO token โ
Each hop in the chain:
- Validates the incoming token's audience (must match this server)
- Exchanges it via OBO for a new token targeted at the next service
- Preserves the original user's identity in the new token's claims
- Triggers a fresh Conditional Access evaluation (if configured in Entra ID)
OBO Configuration
export HELM_MCP_OBO_TOKEN_URL="https://login.microsoftonline.com/{tenant}/oauth2/v2.0/token"
export HELM_MCP_OBO_CLIENT_ID="helm-mcp-app-id"
export HELM_MCP_OBO_CLIENT_SECRET="helm-mcp-client-secret"
Why Not Forward the Token?
Forwarding a user's token to downstream services is tempting but problematic. The MCP Security Best Practices explicitly discourages it. With OBO, each service gets a token minted for its own audience, scoped to only the permissions it needs. If a token is intercepted, the blast radius is limited to a single service rather than the entire chain.
AWS EKS and OBO Support
AWS EKS 1.34+ with OIDC
AWS EKS supports OIDC identity providers for cluster authentication starting from EKS 1.21, with significant improvements in 1.34+. However, EKS does not natively support the Entra ID OBO flow for Kubernetes API authentication. The authentication patterns differ:
| Pattern | Supported | Details |
|---|
| EKS OIDC Identity Provider | Yes | Configure Entra ID as an OIDC provider in EKS. Users authenticate directly with Entra ID tokens where aud = EKS cluster. No OBO needed โ the token is issued directly for the cluster. |
| IRSA (IAM Roles for Service Accounts) | Yes | Pod-level identity via projected service account tokens. This is M2M (client credentials), not user-delegated. |
| EKS Pod Identity | Yes (EKS 1.34+) | Simplified pod identity using EKS Pod Identity Agent. Also M2M, not user-delegated. |
| OBO โ Kubernetes API | Partial | Entra ID OBO can issue tokens for any registered resource. If EKS is configured with Entra ID as an OIDC provider and the Kubernetes API is registered as an app in Entra ID, OBO-issued tokens can authenticate to EKS. Requires custom --oidc-issuer-url, --oidc-client-id, and --oidc-username-claim configuration on the EKS OIDC provider. |
Recommended pattern for EKS: Configure Entra ID as the EKS OIDC identity provider. The MCP client authenticates the user and obtains a token with aud = helm-mcp. helm-mcp validates this token, then performs an OBO exchange to get a new token with aud = EKS cluster OIDC client ID. This OBO-issued token is used for Kubernetes API calls, preserving user identity and enabling per-user RBAC.
AWS Labs MCP and OBO
AWS Labs MCP servers (e.g., awslabs/mcp) and Amazon Bedrock AgentCore do not implement OAuth2 OBO or RFC 8693 Token Exchange. AgentCore uses a different model:
- User identity propagation: Via an opaque
X-Amzn-Bedrock-AgentCore-Runtime-User-Id HTTP header โ not a cryptographically signed token
- Outbound authentication: OAuth Authorization Code (3Lo) or Client Credentials (2Lo), but these are separate auth events, not delegated identity propagation
- Token Vault: Stores refresh tokens for third-party services, but this is agent-scoped, not user-delegated
This means AWS Labs MCP servers cannot participate in an Entra ID OBO chain natively. If your architecture requires user-delegated identity propagation through AWS-hosted MCP servers, you must implement OBO exchange as a custom middleware layer, or use helm-mcp's built-in OBO support as a reference implementation.
Forward Proxy Support
helm-mcp respects standard proxy environment variables:
export HTTP_PROXY=http://proxy.example.com:8080
export HTTPS_PROXY=http://proxy.example.com:8080
export NO_PROXY=localhost,127.0.0.1,.internal.company.com
Development
Prerequisites
- Go 1.27+
- Python 3.12+ (for the Python package)
- golangci-lint v2 (optional, for linting)
Build
make build
make install
make build-all
Test
make test
make test-short
cd python && pip install -e ".[dev]" && pytest -v tests/
Lint
Security Check
Coverage
Architecture
cmd/helm-mcp/ Entry point, transport selection, CLI flags
internal/
helmengine/ Engine interface and shared types
v3/ Helm v3 SDK implementation
v4/ Helm v4 SDK implementation
tools/ MCP tool handlers
release/ Install, upgrade, uninstall, rollback, list, status, etc.
chart/ Create, lint, template, package, pull, push, show, etc.
repo/ Add, list, update, remove, index
registry/ Login, logout
search/ Hub, repo
plugin/ Install, list, uninstall, update
env/ Env, version
security/ Process hardening, input validation, credential scrubbing
resilience/ Response budget, circuit breaker, retry, timeouts, manifest sanitisation
server/ MCP server creation and tool registration
python/ FastMCP-based Python wrapper
src/helm_mcp/ Python package source
tests/ Python tests
Contributing
We welcome contributions from the community! Whether it's bug reports, feature requests, documentation improvements, or code contributions โ all help is appreciated.
See CONTRIBUTING.md for detailed guidelines on:
- Setting up your development environment
- Running tests and linters
- Submitting pull requests
- Commit message conventions
License
This project is licensed under the MIT License โ free to use, modify, and distribute.