Bazel Central Registry MCP server

The repository exposes a Model Context Protocol (MCP) server that provides programmatic access to module information. It is implemented using FastMCP.

Running the server

Use Bazel to start the server, no Python virtual environment setup needed:

bazel run //tools:mcp_server

Available tools

The server registers a set of MCP tools mirroring the functionality of tools/registry.py:

• list_modules() – list all module names in the registry
• search_modules(pattern) – search module names using a regex
• list_versions(module, include_yanked=False) – list versions for a module
• get_metadata(module) – return the module's metadata.json
• get_source(module, version) – return source.json for a version
• get_patch_file(module, version, patch_name) – return the patch file content for a given patch
• get_module_bazel(module, version) – return the MODULE.bazel file
• get_presubmit_yaml(module, version) – return presubmit.yml if present
• get_attestations(module, version) – return attestations.json if present
• get_registry_info() – return the contents of bazel_registry.json

Set up with Gemini CLI

Add the server to Gemini CLI's settings.

  "mcpServers": {
    "BCR": {
      "command": "bazel",
      "args": ["run", "//tools:mcp_server"],
      "cwd": "<Your local path to this repository>",
      "timeout": 5000,
      "trusted": true
    }
  }

Make sure to build the target first to reduce startup time.

Example prompts

• Update all Bazel modules in my MODULE.bazel file.
• What are the dependencies in the latest protobuf version?
• Any version of rules_cc was yanked?
• Show me all modules starting with “rules_”
• Show me the source.json of the latest version of rules_go.
• On which platforms was zlib tested?
• Does the latest rules_cc version have attestations?
• Who are the maintainers of rules_python?