agentmods.dev

Ctxlint AGENTS.md

A contributor guide for Ctxlint, a tool that checks project instruction files such as AGENTS.md and CLAUDE.md for configuration and content problems.

In plain words
What is it for?
Use it to install dependencies, run all or selected Vitest tests, configure checks and ignored files, add supported context-file types, and understand lint rules.
Why use it?
It explains how the project is configured, how its checks and rules work, and how to run its automated tests, reducing guesswork when changing the tool.

Instructions file for CodexOpenCode

11 4mo ago A scan 790 tokens original MIT
View the source file ctxlint/Ctxlint
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add instructions/ctxlint/ctxlint/agents-md
Clone the repo
git clone --depth 1 https://github.com/ctxlint/Ctxlint

Made for: Codex, OpenCode.

Per session 790 This file is loaded in full into every session.
When invoked 790 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00790 $0.00790
Opus 5 $0.00395 $0.00395
Sonnet 5 $0.00158 $0.00158
Haiku 4.5 $0.00079 $0.00079

Measured 2d ago against content hash 00cdf90415dd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Ctxlint AGENTS.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

AGENTS.md · 52 lines

How it starts

The opening of the file, as written. The whole thing — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md

Build & test

  • Install: npm install
  • Test: npm test (vitest, 118 tests)
  • Single test: npx vitest --filter <name>
  • No lint config — use standard JS style

Architecture

Configuration

  • Project-level config lives in .ctxlintrc or .ctxlintrc.json at the project root.
  • src/config.js loads and merges config with defaults. Fields: checks, ignore, strict, contextFiles, tokenThresholds.
  • CLI flags always override .ctxlintrc settings.
  • --strict mode exits 1 on warnings (not just errors). Can be set in .ctxlintrc or via CLI.

Context file linting

  • Rules live in src/rules/. Each exports: { name, severity, description, run(parsedFile, projectData) → Diagnostic[] }
  • token-budget runs last in check.js — it receives all other diagnostics to calculate signal-to-noise ratio.
  • Supported context files: AGENTS.md, CLAUDE.md, GEMINI.md, .github/copilot-instructions.md, .windsurfrules, .clinerules, .aiderules, CONVENTIONS.md — defined in src/constants.js. Additional files can be added via the contextFiles field in .ctxlintrc.
  • Test fixtures in test/fixtures/ are real directory structures, not mocks. Tests use the actual filesystem.
  • Token estimation uses 4 chars/token heuristic, not a real tokenizer.

MCP config linting

  • MCP rules live in src/rules/mcp/. Each exports: { name, severity, description, run(parsedConfig) → Diagnostic[] }
  • MCP diagnostics have { rule, severity, server, field, message, suggestion } — note server and field instead of line.
  • MCP config detection in src/detector/mcp.js — checks for .mcp.json, .cursor/mcp.json, .vscode/mcp.json, and .amazonq/mcp.json in the project root.
  • mcp-env-syntax rule validates that env var references use the correct syntax per client: VS Code requires ${env:VAR}, not ${VAR}. Rule receives configName (the file path) to determine the client.
  • MCP reporter in src/reporter/mcp-terminal.js (terminal + JSON).

Commands

  • check — lints context files. Supports --format terminal|json|sarif, --watch, and --strict.
  • mcp — lints MCP config files. Supports --format terminal|json.
  • init — generates a minimal context file from project metadata.
  • slim — removes error-severity flagged content in place.
  • diff — finds drift between context file and git history.

Read the full file on GitHub · 52 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 52 lines · 790 tokens per session scan A 00cdf90415dd

Subscribe to this mod's changes

Ctxlint AGENTS.md is an instructions file published in the GitHub repository ctxlint/Ctxlint (11 stars, last pushed 4mo ago), licensed MIT. It adds 790 tokens to every session, about $0.0040 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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