{
  "markdown": "<p align=\"center\">\n  <img src=\"assets/brand/logo-mark-128.png\" width=\"96\" alt=\"CallLint logo\" />\n</p>\n\n# CallLint\n\n**Your agent can run tools faster than you can review them.**\n\nCallLint is a pre-flight risk linter for MCP and agent-tool configs. It checks\nthe blast radius before the tool runs: what each tool can read, write, execute,\nconnect to, send, or mutate — then returns an evidence-backed verdict\n(**SAFE / REVIEW / BLOCK / UNKNOWN**) before your agent ever loads the server.\n\nIt never executes, installs, or connects to the servers it judges.\n\n```bash\nnpx calllint scan .cursor/mcp.json\n```\n\n> Status: 1.9.1 stable CLI release. Actively hardened. Verdicts are heuristic\n> decision support, not a safety guarantee. Read [Limitations](#limitations)\n> before relying on a verdict for a security decision.\n\n```text\n$ npx calllint scan .cursor/mcp.json\nresult: BLOCK   (BLOCK 1 · UNKNOWN 0 · REVIEW 0 · SAFE 0)\n\nBLOCK  helpful-notes    PROMPT · SUPPLY\n  • [BLOCKER] Model-directed instruction in tool metadata\n      evidence: tools.save_note.description = \"do not tell the user\"\n  • Package version is not pinned\n      evidence: package = helpful-notes@latest\n  autonomous use: deny · manual approval: required\n```\n\n## What is CallLint?\n\nAn agent's power is the union of its tools' permissions. A single MCP server can\nadd filesystem write, shell execution, network egress, or model-directed\ninstructions to an autonomous agent — usually described only by untrusted,\ntool-provided metadata. CallLint inspects that surface statically and tells you,\nwith evidence, what you would be granting **before** you grant it.\n\n- **Deterministic** — same input, same verdict. No model in the decision path.\n- **Offline by default** — no network unless you pass `--online` (advisory only).\n- **Evidence-backed** — every finding cites the exact config field it came from.\n- **Never executes the target** — it reasons about configuration, not behavior.\n\n## What it checks\n\nCallLint runs thirteen static detectors over each server entry:\n\n| Detector | Risk symbol | What it flags |\n|---|---|---|\n| `secretEnvKeys` | 🔐 Secrets | Env keys whose names imply credentials (tokens, keys, passwords), incl. docker inline `-e KEY` |\n| `broadFilesystemPath` | 📁 Files | Filesystem roots that grant broad read/write (`/`, `~`, home, drive roots), incl. docker bind-mount host paths |\n| `unknownRemote` | 🌐 Network | Remote/HTTP transports to unrecognized or unpinned hosts |\n| `promptPoisoning` | 🧠 Prompt | Model-directed instructions hidden in tool names, descriptions, or schemas |\n| `hiddenInstructions` | 🧠 Prompt | Hidden/obfuscated content (zero-width, bidi, tag-char, HTML comments) in model-visible metadata |\n| `dangerousCommand` | ⚙️ Exec | Shell-out / interpreter / package-runner commands (`bash -c`, `npx`, …) |\n| `unverifiedLocalSource` | ⚙️ Exec | Local script/binary that is not a recognized package, pinned image, or remote |\n| `externalMutation` | ✉️ Action | Tools that send or mutate external state (email, messages, posts) |\n| `messagingSend` | ✉️ Action | Tools that send messages/email on your behalf (Slack, Twilio, SMTP, …) |\n| `oauthScope` | ✉️ Action | OAuth scopes that are undeclared, broad, or expansive (`admin`, `*`, `repo`, …) |\n| `gatewayRuntime` | ✉️ Action | Long-running gateway runtimes that proxy many downstream tools under one auth |\n| `financialAction` | 💸 Money | Payment / transfer / irreversible financial actions |\n| `unpinnedPackage` | 🧩 Supply | Unpinned package specs (`@latest`, no version) — rug-pull surface |\n\nFindings roll up into a **risk class** (S0 metadata-only → S5\nfinancial/irreversible) and an aggregate **verdict** per server and per config.\n\nDrift detection (`baseline` / `verify`) records an approved risk surface and\nflags **rug-pulls** (🔁) — a previously-approved server whose risk surface later\nchanged.\n\n## What it does not check\n\nThis list matters more than the feature list. CallLint is a *pre-flight check*,\nnot a proof of safety.\n\n- It **does not execute, install, or connect** to servers — so it cannot observe\n  actual runtime behavior (what a server really reads, writes, or sends).\n- It **does not read or validate secret values** — it inspects config *shape*\n  (key names), never the contents of your `.env` or credential stores.\n- It **does not analyze server source code** — only the configuration and any\n  tool metadata you provide under `x-calllint.tools`.\n- It **does not fetch anything** unless you pass `--online`, and online results\n  are advisory — they never upgrade a verdict toward SAFE.\n- It **does not certify** third-party tools, replace human security review, or\n  guarantee an agent is safe.\n- A clean run is **necessary, not sufficient.** Pair it with code review,\n  least-privilege tokens, and runtime controls.\n\n`UNKNOWN` is a real verdict: when CallLint cannot verify what a server will do,\nit says so and never silently upgrades `UNKNOWN` to `SAFE`.\n\n### What CallLint is — and is not\n\n| CallLint is **not** | CallLint **is** |\n|---|---|\n| a runtime sandbox | a pre-run risk linter for agent-tool configs |\n| a secret scanner (it never reads secret values) | a config-shape inspector that flags credential-shaped keys |\n| `npm audit` (known package CVEs) | a blast-radius check on the authority you are granting |\n| a server source-code analyzer | a static config + tool-metadata analyzer |\n| a safety certificate | heuristic decision support, not a safety guarantee |\n| a replacement for human review | the start of a review, with evidence attached |\n\n## Install\n\n```bash\n# run without installing (recommended):\nnpx calllint scan ./mcp.json\n\n# or install globally:\nnpm install -g calllint\n```\n\nRequires Node.js ≥ 20. The published package is a single self-contained bundle\nwith zero runtime dependencies. `calllint` on the `latest` tag is the current\nstable CLI release; `@next` carries release candidates and `@preview`\nolder previews.\n\n## Quick start\n\n**Zero-config scanning** — discover and scan all your agent configs:\n\n```bash\n# Auto-discover and scan all agents (Cursor, Claude Code, Claude Desktop, VS Code, Windsurf)\ncalllint scan --auto\n\n# List all discovered agent configs\ncalllint inventory\n\n# Scan a specific agent type\ncalllint scan --agent cursor\ncalllint scan --agent vscode\n```\n\n**Manual path scanning** — scan a specific config file:\n\n```bash\n# scan a config file (auto-detects common locations if no path given)\ncalllint scan ./mcp.json\n\n# scan from stdin, machine-readable JSON out\ncat .cursor/mcp.json | calllint scan --stdin --json\n\n# CI gate: non-zero exit per policy (BLOCK=30, UNKNOWN=20, REVIEW=10 if enabled)\ncalllint scan ./mcp.json --ci --no-emoji\n\n# synthesize a config for an npm package (offline) or a GitHub repo (--online)\ncalllint scan npm:mcp-weather@1.0.0\ncalllint scan github:owner/repo --online\n\n# record an approved baseline, then detect drift / rug-pulls later\ncalllint baseline ./mcp.json\ncalllint verify ./mcp.json --ci\n\n# explain one server's verdict from the last scan\ncalllint explain filesystem\n\n# structured diagnostics for editor / agent-host integration\ncalllint diagnostics ./mcp.json --json\n```\n\nOutput formats: default terminal, `--compact`, `--json` (stable schema),\n`--sarif` (GitHub Code Scanning), `--markdown` (PR comments / GitHub Step\nSummary), `--html` (self-contained report). The\n`diagnostics` command emits a separate editor/agent-host JSON\n(`calllint.diagnostics.v0`).\n\nSee CallLint running in CI on a deliberately risky config —\n[`calllint-demo-risky-mcp`](https://github.com/calllint/calllint-demo-risky-mcp)\npublishes one Code Scanning alert per finding on every push.\n\n## Beyond config scanning\n\nThe same engine and verdict semantics extend past MCP-config scanning to other\npoints where an agent grants authority:\n\n```bash\n# Preflight a planned external action before the agent runs it\ncalllint action inspect payment.json          # calllint.action.v0 descriptor\ncalllint action inspect email-reply.json --json\n\n# Preflight a normalized agent inbox event (delegates to the action analyzer)\ncalllint inbox inspect gmail-reply.normalized.json\n\n# Record a scan as a local, verifiable receipt, then validate it later\ncalllint scan ./mcp.json --receipt            # writes calllint-receipt.json\ncalllint receipt verify calllint-receipt.json\n\n# Attach an external content-scanner report as evidence (joint Trust Packet)\ncalllint scan ./mcp.json --evidence skillspector-report.json\n```\n\nReceipts (`calllint.receipt.v0`) are a reporting layer derived from a scan —\nthey prove which CallLint version produced which verdict over which input under\nwhich policy. They are not a second scanner and never re-judge a verdict. A\nreceipt can carry an optional ed25519 signature; `receipt keygen` / `receipt\nsign` generate and sign one locally for development, and `receipt verify`\nchecks the signature when present (offline, with `--public-key`). A signature\nproves provenance and integrity — never safety.\n\n## Trust Gateway — prepare, approve, apply, verify\n\nScanning tells you the blast radius; the Trust Gateway acts on it, safely. It\nresolves an agent-tool target to an immutable, digest-pinned identity, judges it\ndeterministically, and emits a **reversible install plan**. Applying that plan is\nthe only thing that ever writes live config: it re-validates every digest, writes\natomically, verifies the result, and rolls back on failure. The gateway never\nexecutes, installs, or connects to the target it judges.\n\n```bash\n# read-only: resolve + judge a target and emit a reversible plan (touches no live config)\ncalllint trust prepare github:owner/repo --host claude-code --write-plan\ncalllint trust show    .calllint/plans/<plan-id>.json\ncalllint trust explain .calllint/plans/<plan-id>.json\n\n# the only writer of live config — applies an approved plan, atomically and reversibly\ncalllint trust apply --plan .calllint/plans/<plan-id>.json --approve <plan-digest> --receipt\n\n# validate a decision receipt later (read-only; never re-judges or executes)\ncalllint trust verify calllint-decision-receipt.json --public-key key.pub\n```\n\nThe gateway is a deterministic, fail-closed pipeline over six sealed digests\n(artifact → evidence → authority → decision/policy → install-plan → receipt). An\napproval binds all six at once; if any digest changes between prepare and apply,\nthe approval is void and nothing is written. `UNKNOWN` never becomes `SAFE`, and\nexternal evidence can tighten a verdict but never set it alone. Five Tier-A hosts\nship the audited apply surface — Claude Code, Cursor, Windsurf, Claude Desktop, and\nVS Code. See the\n[CHANGELOG](CHANGELOG.md) (Trust Gateway Core) and ADRs 0035–0039.\n\n## Continuous Guard — catch a rug-pull after approval\n\nA tool you approved once can change later. `calllint guard` records the approved\nauthority surface and re-decides it — **silent when nothing changed**, and loud the\nmoment a previously-approved server's risk surface shifts (a rug-pull, 🔁). It adds\nno new verdict engine: it reuses the same deterministic drift check as\n`baseline` / `verify` and the same stable exit codes.\n\n```bash\n# re-assess the current authority surface vs the approved baseline (silent when unchanged)\ncalllint guard\n\n# install a guard hook into a host — a declarative shim that only shells out to `calllint guard`\ncalllint guard install --host git       # git pre-commit hook\ncalllint guard install --host github    # GitHub Actions drift-gate workflow\ncalllint guard status                   # baseline / disable / installed-hook state\ncalllint guard disable                  # writes .calllint/guard.json { enabled: false }\n```\n\nGuard installs on seven hosts: `git` (pre-commit), `git-pre-push`, `github`\n(Actions), `claude-code`, `copilot`, `gemini`, and `vscode`. Every hook binds\n**only** to a commit / push / CI / session-start event — never a per-call gate — so\na guard hook can never silently block a tool call (ADR 0045, ADR 0052). Hosts with a\ndedicated file (git, GitHub, Copilot) are written whole; hosts whose hook lives\ninside a shared user-owned config (Claude Code, Gemini, VS Code) get a fragment\nprinted for you to merge — `guard install` never clobbers a shared file.\n\n## Install the preflight into your agent — `integrate` and the Claude plugin\n\n`calllint integrate` installs CallLint's own MCP server (`calllint-mcp`) into the\nagent hosts you already use, so the agent can run the preflight itself before it\napproves another server. It is **plan-only by default**: it detects installed hosts,\nbuilds a reversible install plan, prints it with a digest, and writes nothing.\nApplying is a separate, explicit, approved step that reuses the Trust Gateway's exact\naudited writer (re-validate → atomic write → verify → roll back on failure).\n\n```bash\ncalllint integrate                       # detect hosts + print an install plan (writes nothing)\ncalllint integrate --write-plan          # persist each plan to .calllint/plans/<id>.json\ncalllint integrate --apply --plan <p.json> --approve <plan-digest>   # the only writer\n```\n\nIt is idempotent (a host that already has the `calllint` server yields no change) and\nproject-scoped (it acts on configs under the repo you run it in, not your global\nmachine state).\n\nFor Claude Code, CallLint also ships as a **plugin** with a `PreToolUse` hook. When\nClaude is about to write or edit an agent-tool config, the hook surfaces a one-line\nrecommendation to scan first. It is **advisory and non-blocking**: it always exits 0,\nnever vetoes a tool call, runs no scan itself, and neither the hook nor an LLM ever\nenters the verdict path (ADR 0051). Installing it does not install a runtime blocker.\n\n```\n/plugin marketplace add calllint/calllint\n/plugin install calllint@calllint\n```\n\n## Run CallLint as an MCP server (`calllint-mcp`)\n\nCallLint also ships as its own MCP server, so an agent can run the preflight\ncheck itself — *before* it installs or approves another MCP server. It is a thin\nwrapper over the same engine: every tool delegates to `calllint`, it carries zero\nruntime dependencies, and it never executes the server it judges.\n\n```jsonc\n{\n  \"mcpServers\": {\n    \"calllint\": {\n      \"command\": \"npx\",\n      \"args\": [\"-y\", \"calllint-mcp\"]\n    }\n  }\n}\n```\n\nTools exposed: `scan_mcp_config_path`, `scan_mcp_config_json`, `verify_baseline`,\n`explain_finding`, `generate_agent_rule`, `generate_ci_gate_snippet`. The server\nspeaks stdio JSON-RPC and returns the same evidence-backed\nSAFE / REVIEW / BLOCK / UNKNOWN verdicts as the CLI. See\n[`packages/calllint-mcp`](packages/calllint-mcp) for details. Published on npm as\n[`calllint-mcp`](https://www.npmjs.com/package/calllint-mcp).\n\n## Example report\n\n```\nCallLint scan\nconfig: ./mcp.json\nresult: BLOCK   (BLOCK 1 · UNKNOWN 0 · REVIEW 0 · SAFE 0)\n────────────────────────────────────────────────────────────\n\nBLOCK  helpful-notes    PROMPT\n  S2 Sensitive read · reproducibility HIGH · confidence medium\n  \"helpful-notes\" is blocked. Risk: Prompt (S2 Sensitive read).\n\n  • [BLOCKER] Suspicious model-directed instruction in tool metadata\n      (prompt.poisoning, observed, confidence medium)\n      evidence: tools.save_note.description = do not tell the user\n      impact: Tool metadata reaches the model directly and can hijack\n              autonomous tool selection or coerce data disclosure.\n      fix: Remove model-directed instructions from tool names,\n           descriptions, schemas, and server instructions.\n\n  autonomous use: deny · manual approval: required · sandbox: recommended\n```\n\n## Corpus and release gate\n\nCallLint's verdicts are tested against a machine-checkable corpus. Each case\npins an expected verdict, required evidence, and a \"dangerous input never\nresolves to SAFE\" policy. The corpus is enforced as a release gate:\n`pnpm corpus:test`.\n\n- 60 calibrated cases\n- 38 real or redacted snapshots\n- 0 dangerous false-SAFE\n- UNKNOWN ratio 10.0% (target ≤ 15%)\n\nThe corpus is a regression and calibration gate, not a claim of full MCP\necosystem coverage. See\n[`project-facts.json`](project-facts.json) (the single source of\ntruth for these numbers). Website and README copy is kept in sync by\n`pnpm check:public-copy`.\n\n## Rule list\n\nEach rule has a detector and a human-readable doc under\n[`packages/risk-engine/rules/`](packages/risk-engine/rules/):\n\n- `prompt.poisoning` — model-directed instructions in tool metadata (blocker)\n- `prompt.hidden-instructions` — hidden/obfuscated content (zero-width, bidi,\n  tag-char, HTML comments) in model-visible metadata (R4 prompt surface, ADR 0014)\n- `prompt.surface-instructions` — model-directed or hidden content in a project\n  document read via `--surface-dir` (README.md / SKILL.md / AGENTS.md /\n  `package.json` description); non-blocker, ADR 0015\n- `exec.dangerous-command` — shell-out / interpreter / package-runner commands\n- `exec.unverified-local-source` — runs a local script/binary that is not a\n  recognized package, pinned image, or remote (ADR 0011)\n- `files.broad-path` — over-broad filesystem grants, incl. docker bind-mount host\n  paths (`--mount type=bind,src=…`, `-v host:container`; ADR 0012)\n- `supply.unpinned-package` — unpinned package specs (rug-pull surface)\n- plus `secretEnvKeys`, `unknownRemote`, `externalMutation`, `financialAction`\n  detectors (see [What it checks](#what-it-checks))\n\nVerdicts are governed by **policy as code** (`calllint.policy.json`); run\n`calllint policy init` to write the defaults and `calllint policy explain` to see\nthe effective policy.\n\n## Badge\n\n`calllint scan <config> --badge` emits a [shields.io endpoint][endpoint] JSON\nobject so an MCP author can show a truthful CallLint verdict in a README. It is\nbuilt for transparency: the badge shows whatever the verdict is, and **only\n`SAFE` is green** — `REVIEW`, `UNKNOWN`, and `BLOCK` each carry a distinct\nnon-green colour. It is a projection of the aggregate verdict (no schema change),\nand `SAFE` means no blockers observed, not a proof of runtime safety. See\n[badge.md](badge.md) for the wiring and the verdict→colour map.\n\n[endpoint]: https://shields.io/badges/endpoint-badge\n\n## Security model\n\nCallLint is a security tool, so its own boundaries are explicit and auditable.\n\n- **No host execution.** It parses and reasons about configuration only; it never\n  runs the server it judges. (See ADR 0003.)\n- **Treats all config as attacker-controlled.** Tool names, descriptions, and\n  schemas are untrusted input; report rendering escapes them.\n- **Offline by default.** `--online` adds advisory registry lookups only and can\n  never make a verdict *more* permissive.\n- **Deterministic and reproducible.** No model, clock, or network in the decision\n  path; the JSON output schema is stable (`calllint.report.v0`).\n\nFull statement: [SECURITY.md](SECURITY.md) ·\ntrust boundaries: [LIMITATIONS.md](LIMITATIONS.md). Report issues to\nsecurity@calllint.com.\n\n## Anonymous usage telemetry — opt-in, off by default\n\nCallLint collects nothing unless you say yes. Scanning works fully offline with\ntelemetry off, and no verdict ever depends on it.\n\n- **Off by default.** On the first run in an interactive terminal, CallLint asks\n  once. Only an explicit `y`/`yes` enables it; a bare Enter, a timeout, `n`, or\n  EOF all leave it off, and the answer is remembered so you are asked at most\n  once.\n- **Never prompts non-interactively.** In CI, when piped, under `--json`/`--sarif`,\n  or with the kill-switch set, there is no prompt and no collection.\n- **Kill-switch.** `CALLLINT_TELEMETRY=0` (also `false`/`off`) disables every\n  tier regardless of stored state.\n- **Check or change it any time:** `calllint telemetry status` · `enable` ·\n  `disable` · `reset` (rotates the installation ID).\n\nWhat an event may carry: event name, host family (e.g. `cursor`), result\ncategory (e.g. `BLOCK`), duration, input kind, discovery surface, CallLint\nversion, and a random installation ID. The payload is built by an **allowlist**\n— an unlisted field is dropped, not forwarded.\n\n**Never sent:** config contents · file paths · commands · arguments · secret\nvalues · prompts · finding evidence · server names · anything identifying you or\nyour machine.\n\nServer side, the request IP and User-Agent are used only for rate limiting and\nare never persisted; installation IDs are HMAC'd at ingestion and the raw value\nis discarded. There is no raw event log.\n\n## Limitations\n\nCallLint sees configuration, not behavior. It can miss risks a server only\nreveals at runtime, and can flag surface that turns out benign. It depends on\nthe tool metadata you provide being accurate, and a server can change after you\napprove it (use `baseline` / `verify` to catch that). It is heuristic: expect\nboth false positives and false negatives, and treat `REVIEW`/`BLOCK` as the\nstart of a review, not a complete threat assessment. See\n[LIMITATIONS.md](LIMITATIONS.md) for the full trust-boundary document.\n\n## Roadmap\n\n- Broaden config-format coverage (more agent/host config dialects)\n- Richer online supply-chain signals (still advisory, never auto-SAFE)\n- More detectors and tunable policy packs\n- Editor/CI integrations beyond SARIF\n\nCallLint stays focused on pre-run risk linting for agent-tool configurations.\nHosted registries, gateways, and runtime enforcement are outside the current\nrelease scope.\n\n## Project\n\nCallLint is the official Apache-2.0 open-source project published at\n[calllint.com](https://calllint.com),\n[github.com/calllint/calllint](https://github.com/calllint/calllint), and npm\npackages [`calllint`](https://www.npmjs.com/package/calllint) (CLI) and\n[`calllint-mcp`](https://www.npmjs.com/package/calllint-mcp) (MCP server). It is\nmaintainer-led — see [GOVERNANCE.md](GOVERNANCE.md) and\n[CONTRIBUTING.md](CONTRIBUTING.md).\n\n## License\n\nApache-2.0 — see [LICENSE](LICENSE) and [NOTICE](NOTICE). The CallLint name and\nlogo are not licensed with the code; see [TRADEMARKS.md](TRADEMARKS.md).\n",
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