Skip to main content

​
fastmcp.resources.resource

Base classes and interfaces for FastMCP resources.

​
Classes

​
ResourceContent

Wrapper for resource content with optional MIME type and metadata. Accepts any value for content - strings and bytes pass through directly, other types (dict, list, BaseModel, etc.) are automatically JSON-serialized. Methods:

​
to_mcp_resource_contents 

to_mcp_resource_contents(self, uri: AnyUrl | str) -> mcp.types.TextResourceContents | mcp.types.BlobResourceContents
Convert to MCP resource contents type. Args:
  • uri: The URI of the resource (required by MCP types)
Returns:
  • TextResourceContents for str content, BlobResourceContents for bytes

​
ResourceResult

Canonical result type for resource reads. Provides explicit control over resource responses: multiple content items, per-item MIME types, and metadata at both the item and result level. Methods:

​
to_mcp_result 

to_mcp_result(self, uri: AnyUrl | str) -> mcp.types.ReadResourceResult
Convert to MCP ReadResourceResult. Args:
  • uri: The URI of the resource (required by MCP types)
Returns:
  • MCP ReadResourceResult with converted contents

​
Resource

Base class for all resources. Methods:

​
from_function 

from_function(cls, fn: Callable[..., Any], uri: str | AnyUrl) -> FunctionResource

​
set_default_mime_type 

set_default_mime_type(cls, mime_type: str | None) -> str
Set default MIME type if not provided.

​
set_default_name 

set_default_name(self) -> Self
Set default name from URI if not provided.

​
read 

read(self) -> str | bytes | ResourceResult
Read the resource content. Subclasses implement this to return resource data. Supported return types:
  • str: Text content
  • bytes: Binary content
  • ResourceResult: Full control over contents and result-level meta

​
convert_result 

convert_result(self, raw_value: Any) -> ResourceResult
Convert a raw result to ResourceResult. This is used in two contexts:
  1. In _read() to convert user function return values to ResourceResult
  2. In tasks_result_handler() to convert Docket task results to ResourceResult
Handles ResourceResult passthrough and converts raw values using ResourceResult’s normalization. When the raw value is a plain string or bytes, the resource’s own mime_type is forwarded so that ui:// resources (and others with non-default MIME types) don’t fall back to text/plain. The resource’s component-level meta (e.g. ui metadata for MCP Apps CSP/permissions) is propagated to each content item so that hosts can read it from the resources/read response.

​
to_mcp_resource 

to_mcp_resource(self, **overrides: Any) -> SDKResource
Convert the resource to an SDKResource.

​
key 

key(self) -> str
The globally unique lookup key for this resource.

​
register_with_docket 

register_with_docket(self, docket: Docket) -> None
Register this resource with docket for background execution.

​
add_to_docket 

add_to_docket(self, docket: Docket, **kwargs: Any) -> Execution
Schedule this resource for background execution via docket. Args:
  • docket: The Docket instance
  • 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()

​
get_span_attributes 

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