fastmcp.utilities.types

Common types used across FastMCP.

Functions

get_fn_name ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_fn_name(fn: Callable[..., Any]) -> str

get_cached_typeadapter ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L45" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_cached_typeadapter(cls: T) -> TypeAdapter[T]

TypeAdapters are heavy objects, and in an application context we'd typically create them once in a global scope and reuse them as often as possible. However, this isn't feasible for user-generated functions. Instead, we use a cache to minimize the cost of creating them as much as possible.

issubclass_safe ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L123" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

issubclass_safe(cls: type, base: type) -> bool

Check if cls is a subclass of base, even if cls is a type variable.

is_class_member_of_type ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L133" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

is_class_member_of_type(cls: Any, base: type) -> bool

Check if cls is a member of base, even if cls is a type variable.

Base can be a type, a UnionType, or an Annotated type. Generic types are not considered members (e.g. T is not a member of list[T]).

find_kwarg_by_type ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L155" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

find_kwarg_by_type(fn: Callable, kwarg_type: type) -> str | None

Find the name of the kwarg that is of type kwarg_type.

Includes union types that contain the kwarg_type, as well as Annotated types.

create_function_without_params ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L181" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

create_function_without_params(fn: Callable[..., Any], exclude_params: list[str]) -> Callable[..., Any]

Create a new function with the same code but without the specified parameters in annotations.

This is used to exclude parameters from type adapter processing when they can't be serialized. The excluded parameters are removed from the function's annotations dictionary.

replace_type ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L454" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

replace_type(type_, type_map: dict[type, type])

Given a (possibly generic, nested, or otherwise complex) type, replaces all instances of old_type with new_type.

This is useful for transforming types when creating tools.

Args:

• type_: The type to replace instances of old_type with new_type.
• old_type: The type to replace.
• new_type: The type to replace old_type with.

Examples:

>>> replace_type(list[int | bool], {int: str})
list[str | bool]

>>> replace_type(list[list[int]], {int: str})
list[list[str]]

Classes

FastMCPBaseModel ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Base model for FastMCP models.

Image ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L238" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Helper class for returning images from tools.

Methods:

to_image_content ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L289" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_image_content(self, mime_type: str | None = None, annotations: Annotations | None = None) -> mcp.types.ImageContent

Convert to MCP ImageContent.

to_data_uri ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L304" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_data_uri(self, mime_type: str | None = None) -> str

Get image as a data URI.

Audio ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L310" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Helper class for returning audio from tools.

Methods:

to_audio_content ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L347" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_audio_content(self, mime_type: str | None = None, annotations: Annotations | None = None) -> mcp.types.AudioContent

File ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L368" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Helper class for returning file data from tools.

Methods:

to_resource_content ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L407" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

to_resource_content(self, mime_type: str | None = None, annotations: Annotations | None = None) -> mcp.types.EmbeddedResource

ContextSamplingFallbackProtocol ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/utilities/types.py#L491" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}