io.github.gnt-ai/gnt — Model Context Protocol (MCP) Server

This MCP server provides a Git-native policy layer for AI agents. It checks action verdicts against rules that have been approved via pull requests (PRs). The repository is associated with governance and policy-as-code for LLM tools in MCP.

🛠️ Key Features

Git-native policy layer for AI agents
Validates action verdicts against PR-approved rules
Focus on policy-as-code and governance
Topics: ai-agents, ai-safety, governance, mcp, policy-as-code, llm-tools

🚀 Use Cases

Enforce AI action outcomes using repository-managed rules
Require rule approval through PR workflows
Integrate policy checks into LLM-tooling scenarios via MCP

⚡ Developer Benefits

Aligns AI agent behavior with Git-managed governance
Uses a PR review process to approve rules
Targets MCP-based LLM tools and agent workflows

⚠️ Limitations

The provided description does not specify supported tools, authentication details, or configuration options.

Run the setup below once and every agent your team runs has a git-native rulebook it has to check over MCP before it acts, approved the same way your code already is: a merged pull request.

Rules live in your repo as files and ship through normal PRs, not a dashboard click.
Agents call check_action over MCP before anything risky (a refund, a delete, a message to a customer) and get back an allow/block/escalate verdict.
Every rule traces back to the git file and the PR that approved it, so "why did the agent do that" always has a paper trail.

Prefer not to run any of this yourself? The hosted version at gntai.dev does the same thing without you standing up a Postgres instance.

Get started (30 seconds)

bash

npm install -g @gnt-ai/cli
gnt login
gnt connect github
gnt prebrain
# merge the opened PR on GitHub. that merge is the approval

Try it with Docker first

To see a real check_action response before installing Node or npm, clone the repository and run the Docker-only demo:

bash

./demo.sh

It builds the full local stack in an isolated gnt-demo Compose project, seeds an approved refund rule, calls check_action, and prints a curl command you can run again. Without an Anthropic key the real fail-closed path returns needs_human; pass GNT_DEMO_ANTHROPIC_API_KEY=sk-ant-... ./demo.sh to opt in to the model's grounded policy verdict. The demo uses deterministic local embeddings and throwaway localhost-only secrets, so it does not need a ZeroEntropy key.

gnt connect's interactive picker, and what gnt prebrain's draft-PR output looks like

Nothing for gnt prebrain to scan yet? Run gnt init first — it scaffolds rules/ locally with a couple of example rule files so there's something real to look at and edit, and points you at gnt prebrain --starter-packs for a curated pack to start from instead.

That merge lands a rule file in your connected repo, shaped like this:

code

your-repo/
└── rules/
    ├── refund-approval-threshold.md
    └── contract-legal-cc.md

Each file is plain markdown with YAML frontmatter:

markdown

---
title: Never refund over $500 without a manager
status: approved
confidence: 0.91
owner_id: finance-team
source_citations: [...]
source: slack
tags: [refunds, finance]
last_validated_at: 2026-07-20
version: 1
superseded_by: null
approved_by: jane@company.com
approved_at: 2026-07-21T14:03:00Z
created_at: 2026-07-18T09:12:00Z
pr_number: 142
pr_url: https://github.com/your-org/your-repo/pull/142
---

Refunds over $500 need manager sign-off before they go out...

See it in action

There's no captured transcript to show yet (see the gap noted at the bottom of this README). Here's the actual response shape a check_action call returns, straight from the tool's contract:

json

{
  "verdict": "blocked",
  "reason": "Refund exceeds the $500 threshold without manager sign-off (rules/refund-approval-threshold.md)",
  "cited_rules": [
    { "id": "refund-approval-threshold", "title": "Never refund over $500 without a manager" }
  ],
  "rules_retrieved": 3
}

verdict is one of allowed, blocked, or needs_human. needs_human is the fail-closed default: no approved rule covers the action, retrieval failed, or the check couldn't complete. It never guesses.

What it does

One MCP endpoint, five tools:

Tool	What it does
`check_action`	Checks a described action against your approved rules before an agent takes it. Returns `allowed`, `blocked`, or `needs_human` with cited rules and a one-line reason.
`search_rules`	Semantic search over your org's approved rules, optionally filtered by tag. An empty list means no approved rule covers the query.
`get_rule`	Fetches one approved rule by id, with its provenance (who approved it, when, what it was cited from).
`list_skill_packs`	Lists every compiled skill pack version for your org, newest first.
`get_skill_pack`	Fetches a compiled skill pack's manifest and file list by id.

Prerequisites

Requirement	Check	Get it
Node >=22.13	`node --version`	nodejs.org

Install

Method	Command
curl	`curl -fsSL gntai.dev/install.sh \| sh`
npm	`npm install -g @gnt-ai/cli`

gnt needs Node >=22.13. If the CLI fails to start with a version error, update Node first and confirm with node --version.

Common commands

bash

gnt login                # sign in, store an API key locally
gnt init                 # scaffold a local rules/ dir with example rule files
gnt connect github       # connect the repo your rules PRs open against
gnt prebrain             # scan sources, extract candidate rules, open PRs
gnt review               # review rules awaiting approval
gnt status               # show brain status
gnt pull                 # download the latest skill pack
gnt gaps                 # list uncovered queries with no approved rule

Config

Variable	Default	What it controls
`GNT_API_URL`	`https://api.gntai.dev`	API endpoint the CLI and MCP calls hit
`GNT_WEB_URL`	`https://gntai.dev`	Web app used for `gnt login`'s browser step
`GNT_CONFIG_DIR`	`~/.gnt`	Where `credentials.json` and local config live

Privacy

No analytics or telemetry dependency in the CLI or the web app.
gnt prebrain's default extraction mode is cloud, not on-device: your source text goes straight to Anthropic's API (or Vercel AI Gateway with zero-data-retention, if you configure it), never to gnt's own servers. Fully on-device extraction needs --mode local against a local Ollama daemon.
The extracted rule candidates still get sent to gnt's API to open the PR. Raw source text stays off gnt's servers in cloud mode; the resulting rule text doesn't.
Rules live in your connected GitHub repo and in gnt's own database. The MCP tools read from gnt's store, not by cloning your repo on every call.
Self-hosting: apps/api only sends error data to Sentry if you set SENTRY_DSN yourself. Leave it unset and nothing goes out.

Team setup

Who writes rules: anyone with access to your connected repo, either through gnt prebrain (batch-extracted from real sources) or gnt review (hand-proposed).
How approval works: merging the PR is the approval. There's no separate publish step.
What gets committed: rules/<rule-id>.md files with the frontmatter shown above and a plain markdown body.
Catching a malformed rule before it's reviewed: gnt rules lint checks a rule file's frontmatter locally, and gnt-ai/gnt/.github/actions/lint-rules runs the same check as a CI step on your rules repo's own PRs, so a bad frontmatter fails the PR instead of the review.

Troubleshooting

Self-hosting: gnt login's browser step has nowhere to land. gnt login opens a browser to a /cli-login page and polls the API for the resulting key — that page is served by the hosted product's web app, which isn't part of this repo. There's no CLI-only login flow (device code or otherwise) today, and no gnt command to set a key manually. Self-hosting this stack currently means building your own thin frontend for that one route (it just needs to complete the sign-in flow and hand the CLI a key). This is a real, open gap in the self-host path, not a config issue — closing it properly means adding a CLI-only login flow.

ValueError: refusing to start: these settings still have their .env.example placeholder value... A change-me-... string is still sitting in apps/api/.env. The error names every offending field; generate a real value for each and retry.

store fails to start with GNT_STORE_INTERNAL_API_SECRET is not set. apps/store/.env wasn't filled in, or wasn't picked up. Confirm the file exists at that exact path, not still named .env.example.

Every store-to-api call gets rejected with 401 or 403, even though both services are up. STORE_INTERNAL_API_SECRET / APPROVAL_SIGNING_SECRET in apps/api/.env don't byte-for-byte match GNT_STORE_INTERNAL_API_SECRET / GNT_APPROVAL_SIGNING_SECRET in apps/store/.env. This fails closed by design. Regenerate both pairs so the two files agree.

A rule fails to save with an embedding or rerank error. apps/store/.env is missing ZEROENTROPY_API_KEY, or it's still empty. Get a real one from zeroentropy.dev.

Full command reference

code

gnt login
gnt logout
gnt init                 scaffold a local rules/ dir with example rule files (--dir <path>)
gnt connect <app>        github, slack, notion-mcp, monday-mcp, linear-mcp, jira-mcp,
                          sentry-mcp, granola-mcp, zoom-mcp, figma, datadog,
                          gitlab-threads, hubspot, airtable, openclaw, hermes
gnt disconnect <app>
gnt status
gnt billing
gnt review
gnt pull
gnt gaps
gnt prebrain              scan local sources, extract candidate rules, open batched draft
                           PRs (~60 flags for source paths and extraction mode, see
                           `gnt prebrain --help`; --mode cloud|local, cloud is the default)
gnt stale
gnt keys list|create|revoke|rotate
gnt webhook list|create|revoke
gnt org show|rename|invite|remove

Shell completion

bash

# bash, add to ~/.bashrc
eval "$(gnt completion bash)"

# zsh, add to ~/.zshrc
eval "$(gnt completion zsh)"

# fish, add to ~/.config/fish/config.fish
gnt completion fish | source

Learn more

Self-hosting walkthrough, including the production-hardening path: docs/self-hosting/README.md
Security policy: SECURITY.md

Self-hosting is a first-class, fully supported path — Apache-2.0 from day one, run it on your own infra with your own keys, or use the hosted version at gntai.dev. The homepage FAQ and the self-hosting docs both describe this same path; there is no "not today" caveat.

License

Why is this free?

Self-hosting gnt costs you nothing, forever — clone it, run docker compose up, bring your own keys. What we sell is the part self-hosting doesn't give you: hosting at gntai.dev, managed OAuth connectors (GitHub, Slack, Linear, Notion, Zendesk — no app-approval process on your end), and usage-based AI features. If you'd rather run it yourself, that's a fully supported, fully free path, not a crippled trial of the real thing.

Contributing

See CONTRIBUTING.md for dev setup and how to open a PR. Every commit needs a Signed-off-by trailer (git commit -s), the Developer Certificate of Origin instead of a CLA. No separate form, just the flag.

Thanks to everyone who's sent a PR:

io.github.gnt-ai/gnt