MCP Customs
Inspect an MCP server for common security risks before you install it. Offline, zero telemetry.
Install
Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).
mcp-customsclaude mcp add mcp-customs -- npx -y mcp-customs@0.1.1{
"mcpServers": {
"mcp-customs": {
"command": "npx",
"args": [
"-y",
"mcp-customs@0.1.1"
]
}
}
}Documentation
From the project's README on GitHub, refreshed weekly. Links open on GitHub.
mcp-customs
Inspect an MCP server for common security risks before you install it. Runs fully offline. No telemetry, no cloud upload, no account.
npx mcp-customs scan ./some-mcp-server──────────────────────────────────────────────────────
MCP-CUSTOMS INSPECTION REPORT
──────────────────────────────────────────────────────
target ./some-mcp-server
files scanned 14
score 62 / 100
stamp [ REVIEW ]
──────────────────────────────────────────────────────
[HIGH] MCP002 — Unsanitized file path (possible path traversal)
server.js:41 return fs.readFileSync(userPath, 'utf8');
fix: Resolve the path against an allowed base directory ...Why
Developers install MCP servers the way they used to install npm packages — quickly, trusting the name, and moving on. An MCP server can read your files, call your APIs, and execute commands on your behalf. Almost nobody checks what it can actually do before connecting it to their agent.
mcp-customs is the "audit before install" step, run locally, in seconds.
What it checks (v0.1)
| Rule | Severity | What it looks for |
|---|---|---|
| MCP001 | critical | Shell command execution with unsanitized interpolation |
| MCP002 | high | File reads/writes without a path-traversal guard |
| MCP003 | critical | eval() / dynamic code execution |
| MCP004 | high | Hardcoded API keys / credentials |
| MCP005 | critical | Tool descriptions containing hidden-instruction language (prompt injection via the tool's own metadata) |
| MCP006 | medium | Outbound network calls combined with environment-variable reads (possible exfiltration) |
| MCP007 | low | No permissions/scopes declared in the manifest |
These are heuristic, regex-based checks — fast and fully auditable in one sitting, not a dataflow analysis. They will produce false positives and will miss things a deeper analysis would catch. Treat a CLEARED stamp as "nothing obvious," not "verified safe."
CI usage
# .github/workflows/mcp-customs.yml
- run: npx mcp-customs scan . --sarif results.sarif --fail-on high
- uses: github/codeql-action/upload-sarif@v3
with:
sarif_file: results.sarifGet a badge for your README
npx mcp-customs scan . --badge --name your-server-nameRoadmap
- [ ] Publish scan results to a public registry (mcp-customs.dev) with searchable trust scores
- [ ] Dynamic/sandboxed analysis (catch what static checks miss)
- [ ] Python-specific AST checks (current Python rules are regex-only)
- [ ] Community flagging / verification on registry entries
License
Apache-2.0. No open-core trap — this CLI stays free either way. If a hosted registry/dashboard ships later, that's a separate paid product; this tool's local scanning will never require it.
Frequently asked questions
What is MCP Customs?
Inspect an MCP server for common security risks before you install it. Offline, zero telemetry.
How do I install MCP Customs?
It runs on your machine. In Claude Code: claude mcp add mcp-customs -- npx -y mcp-customs@0.1.1. For other clients, paste the JSON configuration from this page into their MCP settings.
Does MCP Customs need an API key?
Its registry entry lists no required key or secret. Some features may still need an account with the service it connects to.
Is MCP Customs open source?
Yes. Its code is on GitHub under the Apache-2.0 license.
Who maintains MCP Customs?
It is published by mcpcustoms. AI.tn lists it but does not maintain or endorse it.
From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.