Pare Cargo ג€” Structured Rust cargo operations (build, test, clippy, fmt, doc) as typed JSON.
io.github.Dave-London/pare-cargo MCP Server
This MCP server, io.github.Dave-London/pare-cargo, provides structured Rust cargo operations—covering build, test, clippy, fmt, and doc—as typed JSON. It is intended to support AI tooling workflows that require consistent, structured outputs rather than untyped command text.
Reliable, structured CLI output for AI agents — no more parsing fragile terminal text.
Pare provides MCP servers that wrap common developer tools (git, npm, docker, test runners, etc.) and return clean, schema-validated JSON instead of raw terminal text. Agents get typed data they can act on directly, without brittle string parsing.
The Problem
Parsing CLI output is fragile. Raw terminal text includes ANSI escape codes, decorative headers, progress bars, locale-specific formatting, and platform differences that break agent workflows in subtle ways. An agent that works fine with git status on macOS may fail on Windows because the output format changed. A test runner's summary line might shift between versions, silently breaking a regex.
Pare eliminates this entire class of errors by returning schema-validated JSON with consistent field names, regardless of platform, tool version, or locale. As a bonus, structured output is significantly smaller — agents use fewer tokens per tool call:
Tool Command
Raw Tokens
Pare Tokens
Reduction
docker build (multi-stage, 11 steps)
373
20
95%
git log --stat (5 commits, verbose)
4,992
382
92%
npm install (487 packages, warnings)
241
41
83%
vitest run (28 tests, all pass)
196
39
80%
cargo build (2 errors, help text)
436
138
68%
pip install (9 packages, progress bars)
288
101
65%
cargo test (12 tests, 2 failures)
351
190
46%
npm audit (4 vulnerabilities)
287
185
36%
Token estimates use ~4 chars/token. The biggest savings appear on verbose commands (builds, installs, tests). For simpler tools like eslint or tsc, the main advantage is reliable structured data — agents can use typed JSON directly rather than parsing strings.
How It Works
Each Pare tool returns two outputs:
content — human-readable text, for MCP clients that display it
structuredContent — typed, schema-validated JSON, ready for agents to process
This uses MCP's structuredContent and outputSchema features to provide type-safe, validated data that agents can rely on without custom parsing.
Example: git status
Raw git output (~118 tokens):
code
On branch main
Your branch is ahead of 'origin/main' by 2 commits.
(use "git push" to publish your local commits)
Changes to be committed:
(use "git restore --staged <file>..." to unstage)
modified: src/index.ts
new file: src/utils.ts
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)
modified: README.md
Untracked files:
(use "git add <file>..." to include in what will be committed)
temp.log
50% fewer tokens. Zero information lost. Fully typed. Savings scale with output verbosity — test runners and build logs see 80–92% reduction.
Available Servers (28 packages, 240 tools)
Install only the servers relevant to your stack — most projects need just 2–4. The full catalog covers a wide range of ecosystems so Pare works wherever you do.
By default, every Pare server registers all of its tools. If a server exposes tools you don't need — or you want to limit which tools are available to an agent — you can filter them with environment variables.
Per-server filter — restrict a single server's tools:
bash
# Only register status and log in the git server
PARE_GIT_TOOLS=status,log npx @paretools/git
Universal filter — restrict tools across all servers:
bash
# Only register these specific tools across any server
PARE_TOOLS=git:status,git:log,npm:install npx @paretools/git
Disable all tools — set the env var to an empty string:
bash
PARE_GIT_TOOLS= npx @paretools/git # no tools registered
Env Var
Scope
Format
Example
PARE_TOOLS
All servers
server:tool,...
git:status,npm:install
PARE_{SERVER}_TOOLS
One server
tool,...
status,log,diff
Rules:
No env var = all tools enabled (default)
PARE_TOOLS (universal) takes precedence over per-server vars
Server names use uppercase with hyphens replaced by underscores (e.g., PARE_MY_SERVER_TOOLS)
Whitespace around commas is ignored
Common patterns:
bash
# Read-only git (no push, commit, add, checkout)
PARE_GIT_TOOLS=status,log,diff,branch,show
# Minimal npm
PARE_NPM_TOOLS=install,test,run
# Only specific tools across all servers
PARE_TOOLS=git:status,git:diff,npm:install,test:run