mcp-blast-radius

# MCP Blast-Radius Auditor

<!-- mcp-name: io.github.aos-standard/mcp-blast-radius -->

[![AOS audited](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/aos-standard/catalog/main/attestations/endpoints/aos-standard__mcp-blast-radius.json)](https://github.com/aos-standard/mcp-blast-radius/blob/main/BADGE_CRITERIA.md)

> **See what any MCP server can actually touch — before you add it to your agent.**

No manifest? You still get the full blast-radius report. Add a manifest to also catch divergences.

> Also, if the server declares a manifest: **Catch an MCP server that touches files it said it wouldn't — and block the merge in CI.**

Statically extract what a third-party MCP server can reach (files, network, subprocess, env) via surface-level analysis. Compare against declared boundaries when a manifest is present.

**Scan scope (default):** production package only — excludes `tests/`, `docs/`, `examples/`, `scripts/`, `benchmarks/`, `.github/`, and `test_*.py` patterns; JSON output includes `scan_scope` and `excluded_file_count`. Pass `--include-peripheral` to scan the full repo.

## Try it in 3 steps

**① Scan your server in one command**

```bash
pip install mcp-blast-radius==0.2.5
mcp-blast-radius-gate --gate-mode advisory --target-dir /path/to/your-mcp-server
```

Point `--target-dir` at your shipping package root (e.g. `src/`). Default scope excludes tests, docs, and scripts.

**② Read the JSON**

| Field | What it means |
|-------|----------------|
| `gate_pass` | Scan finished (`advisory` = report either way; `blocking` = exit 1 on divergences) |
| `blocking_reasons` | Lines starting with `DIVERGENCE:` = declared vs. observed mismatch (if you ship a manifest) |
| `blast_radius` | Static capability surface (network, subprocess, env, filesystem) |
| `confidence` labels | `declared` / `observed-static` / `cannot-determine` — static only, upper bounds |

Undeclared capability is usually drift, not malice. Treat network/subprocess counts as **upper bounds**, not confirmed traffic.

**③ Apply for an audit badge (optional, opt-in)**

Ran a clean scan and want a signed README badge? [Open a badge application](https://github.com/aos-standard/mcp-blast-radius/issues/new?template=badge-application.yml) — paste your command and JSON. Free, 90-day attestation, no phone-home. Criteria: [BADGE_CRITERIA.md](BADGE_CRITERIA.md).

To verify any published attestation independently: `pip install cryptography`, then run `packaging/scripts/verify_attestation.py` (accepts local paths or HTTPS URLs). See [BADGE_CRITERIA.md §Verify](BADGE_CRITERIA.md#verify-any-badge).

---

## Machine-readable metadata

- **Agent Card** (capabilities, limitations, pricing): [agent_card.json](https://raw.githubusercontent.com/aos-standard/mcp-blast-radius/main/packaging/agent_card.json)
- **Catalog entry** (pricing, install, MCP endpoint): [aos-standard/catalog](https://raw.githubusercontent.com/aos-standard/catalog/main/catalog.json)
- **Spec**: [AOS-v0.1](https://github.com/aos-standard/AOS-spec)

## Example walkthrough

```bash
git clone --depth 1 https://github.com/oraios/serena.git /tmp/serena
mcp-blast-radius-gate --gate-mode advisory --target-dir /tmp/serena
```

Inspect `blast_radius` and any `DIVERGENCE:` lines in `blocking_reasons`.

## Report a scan question

[Open a GitHub issue](https://github.com/aos-standard/mcp-blast-radius/issues/new) with your JSON output (structured template loads automatically).

## 30-second scan

```bash
pip install mcp-blast-radius
mcp-blast-radius-gate --gate-mode blocking --target-dir /path/to/mcp-server
```

`pipx run mcp-blast-radius` starts the **MCP stdio server** (for Claude Desktop / Cursor). For CLI scanning, use `mcp-blast-radius-gate` as above.

- **Red (blocking):** divergence detected — code touches paths or capabilities not declared in manifest.
- **Green:** no divergences (or no manifest — blast radius report only, advisory pass).

## Install

```bash
python3 -m venv .venv
source .venv/bin/activate
pip install .
```

## CLI entry

```bash
mcp-blast-radius          # MCP stdio server
mcp-blast-radius-gate     # CI gate (default blocking, exit 1 on fail)
```

### CI blocking gate

```bash
mcp-blast-radius-gate --gate-mode blocking --target-dir .
# no divergences → exit 0 / divergences or declaration violations → exit 1
```

## MCP tools

- `aos_compliance_validate` — scan one MCP server directory (`target_dir` required; `tool_id` optional label)
- `aos_compliance_self_test` — wiring smoke test

Default `gate_mode=advisory`. Use `gate_mode=blocking` in CI to fail on divergences.

## What is extracted

| Layer | Scope | Confidence |
|-------|-------|------------|
| Dependencies | `requirements.txt`, `pyproject.toml`, `package.json` | `declared` |
| Python AST | imports, file I/O, network, env, subprocess; MCP tool attribution | `observed-static` / `cannot-determine` |
| Divergence | manifest `permitted_output_paths` / `oracle_paths` vs observed access | blocking when mismatch |

**Limitations:** Static analysis only. Dynamic imports, `getattr`/`eval`, obfuscation, and native extensions may hide capabilities. We do not claim complete coverage — every finding includes a `confidence` label.

## Environment

| Variable | Purpose |
|----------|---------|
| `AOS_VALIDATOR_TARGET_DIR` | Default scan root when `target_dir` is omitted |
| `AOS_VALIDATOR_MCP_LOG` | JSONL path for local tool call log (never sent externally) |
| `AOS_VALIDATOR_CALLER` | Caller label (`ci`, `smoke_self_call`, etc.) |

## Example

```bash
aos_compliance_validate target_dir=/path/to/my-mcp-server gate_mode=blocking
```

## License

MIT