fastmcp.mcp_config

Canonical MCP Configuration Format.

This module defines the standard configuration format for Model Context Protocol (MCP) servers. It provides a client-agnostic, extensible format that can be used across all MCP implementations.

The configuration format supports both stdio and remote (HTTP/SSE) transports, with comprehensive field definitions for server metadata, authentication, and execution parameters.

Example configuration:

{
    "mcpServers": {
        "my-server": {
            "command": "npx",
            "args": ["-y", "@my/mcp-server"],
            "env": {"API_KEY": "secret"},
            "timeout": 30000,
            "description": "My MCP server"
        }
    }
}

Functions

infer_transport_type_from_url ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L54" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

infer_transport_type_from_url(url: str | AnyUrl) -> Literal['http', 'sse']

Infer the appropriate transport type from the given URL.

update_config_file ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L361" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

update_config_file(file_path: Path, server_name: str, server_config: CanonicalMCPServerTypes) -> None

Update an MCP configuration file from a server object, preserving existing fields.

This is used for updating the mcpServer configurations of third-party tools so we do not worry about transforming server objects here.

Classes

StdioMCPServer ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L168" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

MCP server configuration for stdio transport.

This is the canonical configuration format for MCP servers using stdio transport.

Methods:

to_transport ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L201" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_transport(self) -> StdioTransport

TransformingStdioMCPServer ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L213" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A Stdio server with tool transforms.

RemoteMCPServer ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L217" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

MCP server configuration for HTTP/SSE transport.

This is the canonical configuration format for MCP servers using remote transports.

Methods:

to_transport ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L253" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_transport(self) -> StreamableHttpTransport | SSETransport

TransformingRemoteMCPServer ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L281" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A Remote server with tool transforms.

MCPConfig ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L292" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A configuration object for MCP Servers that conforms to the canonical MCP configuration format while adding additional fields for enabling FastMCP-specific features like tool transformations and filtering by tags.

For an MCPConfig that is strictly canonical, see the CanonicalMCPConfig class.

Methods:

wrap_servers_at_root ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L306" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

wrap_servers_at_root(cls, values: dict[str, Any]) -> dict[str, Any]

If there's no mcpServers key but there are server configs at root, wrap them.

add_server ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L319" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

add_server(self, name: str, server: MCPServerTypes) -> None

Add or update a server in the configuration.

from_dict ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L324" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

from_dict(cls, config: dict[str, Any]) -> Self

Parse MCP configuration from dictionary format.

to_dict ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L328" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_dict(self) -> dict[str, Any]

Convert MCPConfig to dictionary format, preserving all fields.

write_to_file ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L332" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

write_to_file(self, file_path: Path) -> None

Write configuration to JSON file.

from_file ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L338" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

from_file(cls, file_path: Path) -> Self

Load configuration from JSON file.

CanonicalMCPConfig ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L346" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Canonical MCP configuration format.

This defines the standard configuration format for Model Context Protocol servers. The format is designed to be client-agnostic and extensible for future use cases.

Methods:

add_server ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L356" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

add_server(self, name: str, server: CanonicalMCPServerTypes) -> None

Add or update a server in the configuration.