Configuration and settings

PyFMCP has two configuration layers:

1. Process configuration controls how the MCP server starts. It is loaded once from command-line arguments and PYFMCP_* environment variables.
2. Runtime tool settings control individual checks. They are loaded from YAML each time a tool is invoked, so changes take effect without restarting the server.

Process configuration

Setting	Default	Description
tools	all tools	Tools to register: pytest, ruff, and basedpyright.
transport	stdio	MCP transport: stdio or http.
host	localhost	HTTP bind host; used with transport=http.
port	4444	HTTP bind port; used with transport=http.
root_dir	current directory	Project directory checked by tools.
settings_file	pyfmcp.yml	YAML settings filename, resolved relative to root_dir.

For environment variables, prefix the setting name with PYFMCP_, for example PYFMCP_TRANSPORT=http or PYFMCP_ROOT_DIR=/work/project. CLI options take precedence over environment values when both are supplied.

Runtime tool settings

Create the configured settings file in the project root. The top-level keys are tool names; each value is validated when that tool is called:

tools:
  pytest:
    test_args: [-q]
    timeout: 120
  ruff_lint:
    max_diagnostics: 100
    diagnostic_length: 200
    timeout: 60
  basedpyright:
    max_diagnostics: 100
    diagnostic_length: 200
    timeout: 60

Available settings are:

• timeout: optional command timeout in seconds, shared by all tools.
• pytest.test_args: extra arguments appended to pytest invocations.
• ruff_lint.max_diagnostics: optional maximum number of diagnostics returned.
• ruff_lint.diagnostic_length: optional maximum length of each diagnostic message.
• basedpyright.max_diagnostics: optional maximum number of diagnostics returned.
• basedpyright.diagnostic_length: optional maximum length of each diagnostic message.

A missing settings file is valid and means that every tool uses its defaults. An invalid YAML document or an invalid setting raises an explicit configuration error; it is not silently ignored. Settings are passed only to registered tools, and the file is read once per tool invocation.

Selecting tools

By default, all three tools are registered. Restrict registration through process configuration, for example with a CLI value or PYFMCP_TOOLS:

pytest,ruff_lint

Unknown tool names are rejected during startup.