fastmcp.cli.client

Client-side CLI commands for querying and invoking MCP servers.

Functions

resolve_server_spec ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

resolve_server_spec(server_spec: str | None) -> str | dict[str, Any] | ClientTransport

Turn CLI inputs into something Client() accepts.

Exactly one of server_spec or command should be provided.

Resolution order for server_spec:

1. URLs (http://, https://) — passed through as-is. If --transport is sse, the URL is rewritten to end with /sse so infer_transport picks the right transport.
2. Existing file paths, or strings ending in .py/.js/.json.
3. Anything else — name-based resolution via resolve_name.

When command is provided, the string is shell-split into a StdioTransport(command, args).

coerce_value ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L264" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

coerce_value(raw: str, schema: dict[str, Any]) -> Any

Coerce a string CLI value according to a JSON-Schema type hint.

parse_tool_arguments ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L298" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

parse_tool_arguments(raw_args: tuple[str, ...], input_json: str | None, input_schema: dict[str, Any]) -> dict[str, Any]

Build a tool-call argument dict from CLI inputs.

A single JSON object argument is treated as the full argument dict. --input-json provides the base dict; key=value pairs override. Values are coerced using the tool's inputSchema.

format_tool_signature ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L370" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

format_tool_signature(tool: mcp.types.Tool) -> str

Build name(param: type, ...) -> return_type from a tool's JSON schemas.

list_command ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L641" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

list_command(server_spec: Annotated[str | None, cyclopts.Parameter(help='Server URL, Python file, MCPConfig JSON, or .js file')] = None) -> None

List tools available on an MCP server.

Examples:

fastmcp list http://localhost:8000/mcp fastmcp list server.py fastmcp list mcp.json --json fastmcp list --command 'npx -y @mcp/server' --resources fastmcp list http://server/mcp --transport sse

call_command ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L796" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

call_command(server_spec: Annotated[str | None, cyclopts.Parameter(help='Server URL, Python file, MCPConfig JSON, or .js file')] = None, target: Annotated[str, cyclopts.Parameter(help='Tool name, resource URI, or prompt name (with --prompt)')] = '', *arguments: str) -> None

Call a tool, read a resource, or get a prompt on an MCP server.

By default the target is treated as a tool name. If the target contains :// it is treated as a resource URI. Pass --prompt to treat it as a prompt name.

Arguments are passed as key=value pairs. Use --input-json for complex or nested arguments.

Examples:

fastmcp call server.py greet name=World
fastmcp call server.py resource://docs/readme
fastmcp call server.py analyze --prompt data='[1,2,3]'
fastmcp call http://server/mcp create --input-json '{"tags": ["a","b"]}'

discover_command ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L897" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

discover_command() -> None

Discover MCP servers configured in editor and project configs.

Scans Claude Desktop, Claude Code, Cursor, Gemini CLI, Goose, and project-level mcp.json files for MCP server definitions.

Discovered server names can be used directly with fastmcp list and fastmcp call instead of specifying a URL or file path.

Examples:

fastmcp discover fastmcp discover --source claude-code fastmcp discover --source cursor --source gemini --json fastmcp list weather fastmcp call cursor:weather get_forecast city=London