ai-station/.venv/lib/python3.12/site-packages/mcp/client/session.py

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2025-12-25 14:54:33 +00:00
import logging
from datetime import timedelta
from typing import Any, Protocol, overload
import anyio.lowlevel
from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
from pydantic import AnyUrl, TypeAdapter
from typing_extensions import deprecated
import mcp.types as types
from mcp.client.experimental import ExperimentalClientFeatures
from mcp.client.experimental.task_handlers import ExperimentalTaskHandlers
from mcp.shared.context import RequestContext
from mcp.shared.message import SessionMessage
from mcp.shared.session import BaseSession, ProgressFnT, RequestResponder
from mcp.shared.version import SUPPORTED_PROTOCOL_VERSIONS
DEFAULT_CLIENT_INFO = types.Implementation(name="mcp", version="0.1.0")
logger = logging.getLogger("client")
class SamplingFnT(Protocol):
async def __call__(
self,
context: RequestContext["ClientSession", Any],
params: types.CreateMessageRequestParams,
) -> types.CreateMessageResult | types.CreateMessageResultWithTools | types.ErrorData: ... # pragma: no branch
class ElicitationFnT(Protocol):
async def __call__(
self,
context: RequestContext["ClientSession", Any],
params: types.ElicitRequestParams,
) -> types.ElicitResult | types.ErrorData: ... # pragma: no branch
class ListRootsFnT(Protocol):
async def __call__(
self, context: RequestContext["ClientSession", Any]
) -> types.ListRootsResult | types.ErrorData: ... # pragma: no branch
class LoggingFnT(Protocol):
async def __call__(
self,
params: types.LoggingMessageNotificationParams,
) -> None: ... # pragma: no branch
class MessageHandlerFnT(Protocol):
async def __call__(
self,
message: RequestResponder[types.ServerRequest, types.ClientResult] | types.ServerNotification | Exception,
) -> None: ... # pragma: no branch
async def _default_message_handler(
message: RequestResponder[types.ServerRequest, types.ClientResult] | types.ServerNotification | Exception,
) -> None:
await anyio.lowlevel.checkpoint()
async def _default_sampling_callback(
context: RequestContext["ClientSession", Any],
params: types.CreateMessageRequestParams,
) -> types.CreateMessageResult | types.CreateMessageResultWithTools | types.ErrorData:
return types.ErrorData(
code=types.INVALID_REQUEST,
message="Sampling not supported",
)
async def _default_elicitation_callback(
context: RequestContext["ClientSession", Any],
params: types.ElicitRequestParams,
) -> types.ElicitResult | types.ErrorData:
return types.ErrorData( # pragma: no cover
code=types.INVALID_REQUEST,
message="Elicitation not supported",
)
async def _default_list_roots_callback(
context: RequestContext["ClientSession", Any],
) -> types.ListRootsResult | types.ErrorData:
return types.ErrorData(
code=types.INVALID_REQUEST,
message="List roots not supported",
)
async def _default_logging_callback(
params: types.LoggingMessageNotificationParams,
) -> None:
pass
ClientResponse: TypeAdapter[types.ClientResult | types.ErrorData] = TypeAdapter(types.ClientResult | types.ErrorData)
class ClientSession(
BaseSession[
types.ClientRequest,
types.ClientNotification,
types.ClientResult,
types.ServerRequest,
types.ServerNotification,
]
):
def __init__(
self,
read_stream: MemoryObjectReceiveStream[SessionMessage | Exception],
write_stream: MemoryObjectSendStream[SessionMessage],
read_timeout_seconds: timedelta | None = None,
sampling_callback: SamplingFnT | None = None,
elicitation_callback: ElicitationFnT | None = None,
list_roots_callback: ListRootsFnT | None = None,
logging_callback: LoggingFnT | None = None,
message_handler: MessageHandlerFnT | None = None,
client_info: types.Implementation | None = None,
*,
sampling_capabilities: types.SamplingCapability | None = None,
experimental_task_handlers: ExperimentalTaskHandlers | None = None,
) -> None:
super().__init__(
read_stream,
write_stream,
types.ServerRequest,
types.ServerNotification,
read_timeout_seconds=read_timeout_seconds,
)
self._client_info = client_info or DEFAULT_CLIENT_INFO
self._sampling_callback = sampling_callback or _default_sampling_callback
self._sampling_capabilities = sampling_capabilities
self._elicitation_callback = elicitation_callback or _default_elicitation_callback
self._list_roots_callback = list_roots_callback or _default_list_roots_callback
self._logging_callback = logging_callback or _default_logging_callback
self._message_handler = message_handler or _default_message_handler
self._tool_output_schemas: dict[str, dict[str, Any] | None] = {}
self._server_capabilities: types.ServerCapabilities | None = None
self._experimental_features: ExperimentalClientFeatures | None = None
# Experimental: Task handlers (use defaults if not provided)
self._task_handlers = experimental_task_handlers or ExperimentalTaskHandlers()
async def initialize(self) -> types.InitializeResult:
sampling = (
(self._sampling_capabilities or types.SamplingCapability())
if self._sampling_callback is not _default_sampling_callback
else None
)
elicitation = (
types.ElicitationCapability(
form=types.FormElicitationCapability(),
url=types.UrlElicitationCapability(),
)
if self._elicitation_callback is not _default_elicitation_callback
else None
)
roots = (
# TODO: Should this be based on whether we
# _will_ send notifications, or only whether
# they're supported?
types.RootsCapability(listChanged=True)
if self._list_roots_callback is not _default_list_roots_callback
else None
)
result = await self.send_request(
types.ClientRequest(
types.InitializeRequest(
params=types.InitializeRequestParams(
protocolVersion=types.LATEST_PROTOCOL_VERSION,
capabilities=types.ClientCapabilities(
sampling=sampling,
elicitation=elicitation,
experimental=None,
roots=roots,
tasks=self._task_handlers.build_capability(),
),
clientInfo=self._client_info,
),
)
),
types.InitializeResult,
)
if result.protocolVersion not in SUPPORTED_PROTOCOL_VERSIONS:
raise RuntimeError(f"Unsupported protocol version from the server: {result.protocolVersion}")
self._server_capabilities = result.capabilities
await self.send_notification(types.ClientNotification(types.InitializedNotification()))
return result
def get_server_capabilities(self) -> types.ServerCapabilities | None:
"""Return the server capabilities received during initialization.
Returns None if the session has not been initialized yet.
"""
return self._server_capabilities
@property
def experimental(self) -> ExperimentalClientFeatures:
"""Experimental APIs for tasks and other features.
WARNING: These APIs are experimental and may change without notice.
Example:
status = await session.experimental.get_task(task_id)
result = await session.experimental.get_task_result(task_id, CallToolResult)
"""
if self._experimental_features is None:
self._experimental_features = ExperimentalClientFeatures(self)
return self._experimental_features
async def send_ping(self) -> types.EmptyResult:
"""Send a ping request."""
return await self.send_request(
types.ClientRequest(types.PingRequest()),
types.EmptyResult,
)
async def send_progress_notification(
self,
progress_token: str | int,
progress: float,
total: float | None = None,
message: str | None = None,
) -> None:
"""Send a progress notification."""
await self.send_notification(
types.ClientNotification(
types.ProgressNotification(
params=types.ProgressNotificationParams(
progressToken=progress_token,
progress=progress,
total=total,
message=message,
),
),
)
)
async def set_logging_level(self, level: types.LoggingLevel) -> types.EmptyResult:
"""Send a logging/setLevel request."""
return await self.send_request( # pragma: no cover
types.ClientRequest(
types.SetLevelRequest(
params=types.SetLevelRequestParams(level=level),
)
),
types.EmptyResult,
)
@overload
@deprecated("Use list_resources(params=PaginatedRequestParams(...)) instead")
async def list_resources(self, cursor: str | None) -> types.ListResourcesResult: ...
@overload
async def list_resources(self, *, params: types.PaginatedRequestParams | None) -> types.ListResourcesResult: ...
@overload
async def list_resources(self) -> types.ListResourcesResult: ...
async def list_resources(
self,
cursor: str | None = None,
*,
params: types.PaginatedRequestParams | None = None,
) -> types.ListResourcesResult:
"""Send a resources/list request.
Args:
cursor: Simple cursor string for pagination (deprecated, use params instead)
params: Full pagination parameters including cursor and any future fields
"""
if params is not None and cursor is not None:
raise ValueError("Cannot specify both cursor and params")
if params is not None:
request_params = params
elif cursor is not None:
request_params = types.PaginatedRequestParams(cursor=cursor)
else:
request_params = None
return await self.send_request(
types.ClientRequest(types.ListResourcesRequest(params=request_params)),
types.ListResourcesResult,
)
@overload
@deprecated("Use list_resource_templates(params=PaginatedRequestParams(...)) instead")
async def list_resource_templates(self, cursor: str | None) -> types.ListResourceTemplatesResult: ...
@overload
async def list_resource_templates(
self, *, params: types.PaginatedRequestParams | None
) -> types.ListResourceTemplatesResult: ...
@overload
async def list_resource_templates(self) -> types.ListResourceTemplatesResult: ...
async def list_resource_templates(
self,
cursor: str | None = None,
*,
params: types.PaginatedRequestParams | None = None,
) -> types.ListResourceTemplatesResult:
"""Send a resources/templates/list request.
Args:
cursor: Simple cursor string for pagination (deprecated, use params instead)
params: Full pagination parameters including cursor and any future fields
"""
if params is not None and cursor is not None:
raise ValueError("Cannot specify both cursor and params")
if params is not None:
request_params = params
elif cursor is not None:
request_params = types.PaginatedRequestParams(cursor=cursor)
else:
request_params = None
return await self.send_request(
types.ClientRequest(types.ListResourceTemplatesRequest(params=request_params)),
types.ListResourceTemplatesResult,
)
async def read_resource(self, uri: AnyUrl) -> types.ReadResourceResult:
"""Send a resources/read request."""
return await self.send_request(
types.ClientRequest(
types.ReadResourceRequest(
params=types.ReadResourceRequestParams(uri=uri),
)
),
types.ReadResourceResult,
)
async def subscribe_resource(self, uri: AnyUrl) -> types.EmptyResult:
"""Send a resources/subscribe request."""
return await self.send_request( # pragma: no cover
types.ClientRequest(
types.SubscribeRequest(
params=types.SubscribeRequestParams(uri=uri),
)
),
types.EmptyResult,
)
async def unsubscribe_resource(self, uri: AnyUrl) -> types.EmptyResult:
"""Send a resources/unsubscribe request."""
return await self.send_request( # pragma: no cover
types.ClientRequest(
types.UnsubscribeRequest(
params=types.UnsubscribeRequestParams(uri=uri),
)
),
types.EmptyResult,
)
async def call_tool(
self,
name: str,
arguments: dict[str, Any] | None = None,
read_timeout_seconds: timedelta | None = None,
progress_callback: ProgressFnT | None = None,
*,
meta: dict[str, Any] | None = None,
) -> types.CallToolResult:
"""Send a tools/call request with optional progress callback support."""
_meta: types.RequestParams.Meta | None = None
if meta is not None:
_meta = types.RequestParams.Meta(**meta)
result = await self.send_request(
types.ClientRequest(
types.CallToolRequest(
params=types.CallToolRequestParams(name=name, arguments=arguments, _meta=_meta),
)
),
types.CallToolResult,
request_read_timeout_seconds=read_timeout_seconds,
progress_callback=progress_callback,
)
if not result.isError:
await self._validate_tool_result(name, result)
return result
async def _validate_tool_result(self, name: str, result: types.CallToolResult) -> None:
"""Validate the structured content of a tool result against its output schema."""
if name not in self._tool_output_schemas:
# refresh output schema cache
await self.list_tools()
output_schema = None
if name in self._tool_output_schemas:
output_schema = self._tool_output_schemas.get(name)
else:
logger.warning(f"Tool {name} not listed by server, cannot validate any structured content")
if output_schema is not None:
from jsonschema import SchemaError, ValidationError, validate
if result.structuredContent is None:
raise RuntimeError(
f"Tool {name} has an output schema but did not return structured content"
) # pragma: no cover
try:
validate(result.structuredContent, output_schema)
except ValidationError as e:
raise RuntimeError(f"Invalid structured content returned by tool {name}: {e}") # pragma: no cover
except SchemaError as e: # pragma: no cover
raise RuntimeError(f"Invalid schema for tool {name}: {e}") # pragma: no cover
@overload
@deprecated("Use list_prompts(params=PaginatedRequestParams(...)) instead")
async def list_prompts(self, cursor: str | None) -> types.ListPromptsResult: ...
@overload
async def list_prompts(self, *, params: types.PaginatedRequestParams | None) -> types.ListPromptsResult: ...
@overload
async def list_prompts(self) -> types.ListPromptsResult: ...
async def list_prompts(
self,
cursor: str | None = None,
*,
params: types.PaginatedRequestParams | None = None,
) -> types.ListPromptsResult:
"""Send a prompts/list request.
Args:
cursor: Simple cursor string for pagination (deprecated, use params instead)
params: Full pagination parameters including cursor and any future fields
"""
if params is not None and cursor is not None:
raise ValueError("Cannot specify both cursor and params")
if params is not None:
request_params = params
elif cursor is not None:
request_params = types.PaginatedRequestParams(cursor=cursor)
else:
request_params = None
return await self.send_request(
types.ClientRequest(types.ListPromptsRequest(params=request_params)),
types.ListPromptsResult,
)
async def get_prompt(self, name: str, arguments: dict[str, str] | None = None) -> types.GetPromptResult:
"""Send a prompts/get request."""
return await self.send_request(
types.ClientRequest(
types.GetPromptRequest(
params=types.GetPromptRequestParams(name=name, arguments=arguments),
)
),
types.GetPromptResult,
)
async def complete(
self,
ref: types.ResourceTemplateReference | types.PromptReference,
argument: dict[str, str],
context_arguments: dict[str, str] | None = None,
) -> types.CompleteResult:
"""Send a completion/complete request."""
context = None
if context_arguments is not None:
context = types.CompletionContext(arguments=context_arguments)
return await self.send_request(
types.ClientRequest(
types.CompleteRequest(
params=types.CompleteRequestParams(
ref=ref,
argument=types.CompletionArgument(**argument),
context=context,
),
)
),
types.CompleteResult,
)
@overload
@deprecated("Use list_tools(params=PaginatedRequestParams(...)) instead")
async def list_tools(self, cursor: str | None) -> types.ListToolsResult: ...
@overload
async def list_tools(self, *, params: types.PaginatedRequestParams | None) -> types.ListToolsResult: ...
@overload
async def list_tools(self) -> types.ListToolsResult: ...
async def list_tools(
self,
cursor: str | None = None,
*,
params: types.PaginatedRequestParams | None = None,
) -> types.ListToolsResult:
"""Send a tools/list request.
Args:
cursor: Simple cursor string for pagination (deprecated, use params instead)
params: Full pagination parameters including cursor and any future fields
"""
if params is not None and cursor is not None:
raise ValueError("Cannot specify both cursor and params")
if params is not None:
request_params = params
elif cursor is not None:
request_params = types.PaginatedRequestParams(cursor=cursor)
else:
request_params = None
result = await self.send_request(
types.ClientRequest(types.ListToolsRequest(params=request_params)),
types.ListToolsResult,
)
# Cache tool output schemas for future validation
# Note: don't clear the cache, as we may be using a cursor
for tool in result.tools:
self._tool_output_schemas[tool.name] = tool.outputSchema
return result
async def send_roots_list_changed(self) -> None: # pragma: no cover
"""Send a roots/list_changed notification."""
await self.send_notification(types.ClientNotification(types.RootsListChangedNotification()))
async def _received_request(self, responder: RequestResponder[types.ServerRequest, types.ClientResult]) -> None:
ctx = RequestContext[ClientSession, Any](
request_id=responder.request_id,
meta=responder.request_meta,
session=self,
lifespan_context=None,
)
# Delegate to experimental task handler if applicable
if self._task_handlers.handles_request(responder.request):
with responder:
await self._task_handlers.handle_request(ctx, responder)
return None
# Core request handling
match responder.request.root:
case types.CreateMessageRequest(params=params):
with responder:
# Check if this is a task-augmented request
if params.task is not None:
response = await self._task_handlers.augmented_sampling(ctx, params, params.task)
else:
response = await self._sampling_callback(ctx, params)
client_response = ClientResponse.validate_python(response)
await responder.respond(client_response)
case types.ElicitRequest(params=params):
with responder:
# Check if this is a task-augmented request
if params.task is not None:
response = await self._task_handlers.augmented_elicitation(ctx, params, params.task)
else:
response = await self._elicitation_callback(ctx, params)
client_response = ClientResponse.validate_python(response)
await responder.respond(client_response)
case types.ListRootsRequest():
with responder:
response = await self._list_roots_callback(ctx)
client_response = ClientResponse.validate_python(response)
await responder.respond(client_response)
case types.PingRequest(): # pragma: no cover
with responder:
return await responder.respond(types.ClientResult(root=types.EmptyResult()))
case _: # pragma: no cover
pass # Task requests handled above by _task_handlers
return None
async def _handle_incoming(
self,
req: RequestResponder[types.ServerRequest, types.ClientResult] | types.ServerNotification | Exception,
) -> None:
"""Handle incoming messages by forwarding to the message handler."""
await self._message_handler(req)
async def _received_notification(self, notification: types.ServerNotification) -> None:
"""Handle notifications from the server."""
# Process specific notification types
match notification.root:
case types.LoggingMessageNotification(params=params):
await self._logging_callback(params)
case types.ElicitCompleteNotification(params=params):
# Handle elicitation completion notification
# Clients MAY use this to retry requests or update UI
# The notification contains the elicitationId of the completed elicitation
pass
case _:
pass