Tool filtering¶

By default every tool a server exposes is offered to the model. toolFilter narrows that, per server.

"toolFilter": {
  "mode": "include",
  "tools": ["get_current_temperature", "get_forecast"]
}

mode: Either "include" (allow-list) or "exclude" (deny-list). Defaults to "include" when omitted.
tools: Array of exact tool names. Matching is case-sensitive.

Behaviour¶

No toolFilter, or an empty tools array → all tools are loaded.
Include mode → only the listed tools are exposed. A listed tool that the server doesn't have logs a warning; the connection continues.
Exclude mode → everything except the listed tools is exposed.
An invalid mode value stops the bridge at startup with an error.

An invalid mode is fatal

Unlike a failing server, a malformed toolFilter isn't skipped — it exits with status 1. This is deliberate: silently ignoring a broken deny-list would expose tools you meant to block.

Examples¶

Include (default mode)Mixed modes

Only these two tools reach the model.

{
  "mcpServers": {
    "weather": {
      "command": "uv",
      "args": ["--directory", "./mock-weather-mcp-server", "run", "main.py"],
      "toolFilter": {
        "tools": ["get_current_temperature", "get_forecast"]
      }
    }
  }
}

An allow-list on one server, a deny-list on another.

{
  "mcpServers": {
    "weather": {
      "command": "uv",
      "args": ["--directory", "./mock-weather-mcp-server", "run", "main.py"],
      "toolFilter": {
        "mode": "include",
        "tools": ["get_current_temperature"]
      }
    },
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"],
      "toolFilter": {
        "mode": "exclude",
        "tools": ["delete_file", "write_file"]
      }
    }
  }
}