function_prompt

fastmcp.prompts.function_prompt

Standalone @prompt decorator for FastMCP.

Functions

prompt

prompt(name_or_fn: str | Callable[..., Any] | None = None) -> Any

Standalone decorator to mark a function as an MCP prompt.

Returns the original function with metadata attached. Register with a server using mcp.add_prompt().

Classes

DecoratedPrompt

Protocol for functions decorated with @prompt.

PromptMeta

Metadata attached to functions by the @prompt decorator.

FunctionPrompt

A prompt that is a function.

Methods:

from_function

from_function(cls, fn: Callable[..., Any]) -> FunctionPrompt

Create a Prompt from a function.

Args:

• fn: The function to wrap
• metadata: PromptMeta object with all configuration. If provided, individual parameters must not be passed.
• name, title, etc.: Individual parameters for backwards compatibility. Cannot be used together with metadata parameter.

The function can return:

• str: wrapped as single user Message
• list[Message | str]: converted to list[Message]
• PromptResult: used directly

render

render(self, arguments: dict[str, Any] | None = None) -> PromptResult

Render the prompt with arguments.

register_with_docket

register_with_docket(self, docket: Docket) -> None

Register this prompt with docket for background execution.

FunctionPrompt registers the underlying function, which has the user’s Depends parameters for docket to resolve.

add_to_docket

add_to_docket(self, docket: Docket, arguments: dict[str, Any] | None, **kwargs: Any) -> Execution

Schedule this prompt for background execution via docket.

FunctionPrompt splats the arguments dict since .fn expects **kwargs.

Args:

• docket: The Docket instance
• arguments: Prompt arguments
• fn_key: Function lookup key in Docket registry (defaults to self.key)
• task_key: Redis storage key for the result
• **kwargs: Additional kwargs passed to docket.add()