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fastmcp.server.context

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Functions

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set_context 

set_context(context: Context) -> Generator[Context, None, None]

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Classes

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LogData

Data object for passing log arguments to client-side handlers. This provides an interface to match the Python standard library logging, for compatibility with structured logging.

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Context

Context object providing access to MCP capabilities. This provides a cleaner interface to MCP’s RequestContext functionality. It gets injected into tool and resource functions that request it via type hints. To use context in a tool function, add a parameter with the Context type annotation: 
@server.tool
def my_tool(x: int, ctx: Context) -> str:
    # Log messages to the client
    ctx.info(f"Processing {x}")
    ctx.debug("Debug info")
    ctx.warning("Warning message")
    ctx.error("Error message")

    # Report progress
    ctx.report_progress(50, 100, "Processing")

    # Access resources
    data = ctx.read_resource("resource://data")

    # Get request info
    request_id = ctx.request_id
    client_id = ctx.client_id

    # Manage state across the request
    ctx.set_state("key", "value")
    value = ctx.get_state("key")

    return str(x)
State Management: Context objects maintain a state dictionary that can be used to store and share data across middleware and tool calls within a request. When a new context is created (nested contexts), it inherits a copy of its parent’s state, ensuring that modifications in child contexts don’t affect parent contexts. The context parameter name can be anything as long as it’s annotated with Context. The context is optional - tools that don’t need it can omit the parameter. Methods:

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request_context 

request_context(self) -> RequestContext[ServerSession, Any, Request]
Access to the underlying request context. If called outside of a request context, this will raise a ValueError.

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report_progress 

report_progress(self, progress: float, total: float | None = None, message: str | None = None) -> None
Report progress for the current operation. Args:
  • progress: Current progress value e.g. 24
  • total: Optional total value e.g. 100

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read_resource 

read_resource(self, uri: str | AnyUrl) -> list[ReadResourceContents]
Read a resource by URI. Args:
  • uri: Resource URI to read
Returns:
  • The resource content as either text or bytes

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log 

log(self, message: str, level: LoggingLevel | None = None, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
Send a log message to the client. Args:
  • message: Log message
  • level: Optional log level. One of “debug”, “info”, “notice”, “warning”, “error”, “critical”, “alert”, or “emergency”. Default is “info”.
  • logger_name: Optional logger name
  • extra: Optional mapping for additional arguments

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client_id 

client_id(self) -> str | None
Get the client ID if available.

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request_id 

request_id(self) -> str
Get the unique ID for this request.

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session_id 

session_id(self) -> str
Get the MCP session ID for ALL transports. Returns the session ID that can be used as a key for session-based data storage (e.g., Redis) to share data between tool calls within the same client session. Returns:
  • The session ID for StreamableHTTP transports, or a generated ID
  • for other transports.

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session 

session(self) -> ServerSession
Access to the underlying session for advanced usage.

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debug 

debug(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
Send a debug log message.

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info 

info(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
Send an info log message.

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warning 

warning(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
Send a warning log message.

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error 

error(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
Send an error log message.

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list_roots 

list_roots(self) -> list[Root]
List the roots available to the server, as indicated by the client.

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send_tool_list_changed 

send_tool_list_changed(self) -> None
Send a tool list changed notification to the client.

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send_resource_list_changed 

send_resource_list_changed(self) -> None
Send a resource list changed notification to the client.

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send_prompt_list_changed 

send_prompt_list_changed(self) -> None
Send a prompt list changed notification to the client.

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sample 

sample(self, messages: str | list[str | SamplingMessage], system_prompt: str | None = None, include_context: IncludeContext | None = None, temperature: float | None = None, max_tokens: int | None = None, model_preferences: ModelPreferences | str | list[str] | None = None) -> ContentBlock
Send a sampling request to the client and await the response. Call this method at any time to have the server request an LLM completion from the client. The client must be appropriately configured, or the request will error.

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elicit 

elicit(self, message: str, response_type: None) -> AcceptedElicitation[dict[str, Any]] | DeclinedElicitation | CancelledElicitation

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elicit 

elicit(self, message: str, response_type: type[T]) -> AcceptedElicitation[T] | DeclinedElicitation | CancelledElicitation

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elicit 

elicit(self, message: str, response_type: list[str]) -> AcceptedElicitation[str] | DeclinedElicitation | CancelledElicitation

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elicit 

elicit(self, message: str, response_type: type[T] | list[str] | None = None) -> AcceptedElicitation[T] | AcceptedElicitation[dict[str, Any]] | AcceptedElicitation[str] | DeclinedElicitation | CancelledElicitation
Send an elicitation request to the client and await the response. Call this method at any time to request additional information from the user through the client. The client must support elicitation, or the request will error. Note that the MCP protocol only supports simple object schemas with primitive types. You can provide a dataclass, TypedDict, or BaseModel to comply. If you provide a primitive type, an object schema with a single “value” field will be generated for the MCP interaction and automatically deconstructed into the primitive type upon response. If the response_type is None, the generated schema will be that of an empty object in order to comply with the MCP protocol requirements. Clients must send an empty object ("")in response. Args:
  • message: A human-readable message explaining what information is needed
  • response_type: The type of the response, which should be a primitive type or dataclass or BaseModel. If it is a primitive type, an object schema with a single “value” field will be generated.

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get_http_request 

get_http_request(self) -> Request
Get the active starlette request.

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set_state 

set_state(self, key: str, value: Any) -> None
Set a value in the context state.

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get_state 

get_state(self, key: str) -> Any
Get a value from the context state. Returns None if the key is not found.