tool-filter-mcp
Verified Safeby respawn-app
Overview
Filters tools from upstream Model Context Protocol (MCP) servers based on regex deny lists to reduce LLM context pollution.
Installation
npx @respawn-app/tool-filter-mcp --upstream http://localhost:3000/sse --deny ".*_file$"Environment Variables
- AUTH_TOKEN (example for HTTP header expansion)
- CUSTOM_VALUE (example for HTTP header expansion)
- API_KEY (example for passing to upstream stdio server)
- DEBUG (example for passing to upstream stdio server)
Security Notes
The project uses `safe-regex2` to prevent Regular Expression Denial of Service (ReDoS) attacks, which is critical for regex-based filtering. It makes network calls to user-defined upstream MCP servers, which is inherent to its proxy functionality; however, this implies a trust relationship with the specified upstream. No obvious hardcoded secrets or malicious patterns were found.
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