MCP Blast-Radius Auditor

MCP Blast-Radius Auditor

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

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 — paste your command and JSON. Free, 90-day attestation, no phone-home. Criteria: 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.

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Machine-readable metadata

• Agent Card (capabilities, limitations, pricing): agent_card.json
• Catalog entry (pricing, install, MCP endpoint): aos-standard/catalog
• Spec: AOS-v0.1

Example walkthrough

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 with your JSON output (structured template loads automatically).

30-second scan

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

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

CLI entry

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

CI blocking gate

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

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

License

MIT