You'd reach for this when you need to restrict which tools Claude can see from an upstream MCP server. It acts as a proxy between Claude and your actual MCP servers, filtering out specific tools using regex patterns on a deny list. Useful if you're running powerful MCP servers but want to limit surface area for specific use cases or users. For example, you could expose a filesystem server but block delete operations, or allow database queries while hiding admin commands. The regex matching gives you flexible control without modifying the upstream servers themselves.
claude mcp add --transport stdio io.github.respawn-app-tool-filter-mcp -- npx -y @respawn-app/tool-filter-mcp