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from __future__ import annotations
import asyncio
import copy
import datetime
import secrets
from contextlib import AsyncExitStack, asynccontextmanager
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Generic, Literal, TypeVar, cast, overload
import anyio
import httpx
import mcp.types
import pydantic_core
from exceptiongroup import catch
from mcp import ClientSession
from pydantic import AnyUrl
import fastmcp
from fastmcp.client.elicitation import ElicitationHandler, create_elicitation_callback
from fastmcp.client.logging import (
LogHandler,
create_log_callback,
default_log_handler,
)
from fastmcp.client.messages import MessageHandler, MessageHandlerT
from fastmcp.client.progress import ProgressHandler, default_progress_handler
from fastmcp.client.roots import (
RootsHandler,
RootsList,
create_roots_callback,
)
from fastmcp.client.sampling import (
ClientSamplingHandler,
SamplingHandler,
create_sampling_callback,
)
from fastmcp.exceptions import ToolError
from fastmcp.mcp_config import MCPConfig
from fastmcp.server import FastMCP
from fastmcp.utilities.exceptions import get_catch_handlers
from fastmcp.utilities.json_schema_type import json_schema_to_type
from fastmcp.utilities.logging import get_logger
from fastmcp.utilities.types import get_cached_typeadapter
from .transports import (
ClientTransport,
ClientTransportT,
FastMCP1Server,
FastMCPTransport,
MCPConfigTransport,
NodeStdioTransport,
PythonStdioTransport,
SessionKwargs,
SSETransport,
StdioTransport,
StreamableHttpTransport,
infer_transport,
)
__all__ = [
"Client",
"ClientSamplingHandler",
"ElicitationHandler",
"LogHandler",
"MessageHandler",
"ProgressHandler",
"RootsHandler",
"RootsList",
"SamplingHandler",
"SessionKwargs",
]
logger = get_logger(__name__)
T = TypeVar("T", bound="ClientTransport")
@dataclass
class ClientSessionState:
"""Holds all session-related state for a Client instance.
This allows clean separation of configuration (which is copied) from
session state (which should be fresh for each new client instance).
"""
session: ClientSession | None = None
nesting_counter: int = 0
lock: anyio.Lock = field(default_factory=anyio.Lock)
session_task: asyncio.Task | None = None
ready_event: anyio.Event = field(default_factory=anyio.Event)
stop_event: anyio.Event = field(default_factory=anyio.Event)
initialize_result: mcp.types.InitializeResult | None = None
class Client(Generic[ClientTransportT]):
"""
MCP client that delegates connection management to a Transport instance.
The Client class is responsible for MCP protocol logic, while the Transport
handles connection establishment and management. Client provides methods for
working with resources, prompts, tools and other MCP capabilities.
This client supports reentrant context managers (multiple concurrent
`async with client:` blocks) using reference counting and background session
management. This allows efficient session reuse in any scenario with
nested or concurrent client usage.
MCP SDK 1.10 introduced automatic list_tools() calls during call_tool()
execution. This created a race condition where events could be reset while
other tasks were waiting on them, causing deadlocks. The issue was exposed
in proxy scenarios but affects any reentrant usage.
The solution uses reference counting to track active context managers,
a background task to manage the session lifecycle, events to coordinate
between tasks, and ensures all session state changes happen within a lock.
Events are only created when needed, never reset outside locks.
This design prevents race conditions where tasks wait on events that get
replaced by other tasks, ensuring reliable coordination in concurrent scenarios.
Args:
transport:
Connection source specification, which can be:
- ClientTransport: Direct transport instance
- FastMCP: In-process FastMCP server
- AnyUrl or str: URL to connect to
- Path: File path for local socket
- MCPConfig: MCP server configuration
- dict: Transport configuration
roots: Optional RootsList or RootsHandler for filesystem access
sampling_handler: Optional handler for sampling requests
log_handler: Optional handler for log messages
message_handler: Optional handler for protocol messages
progress_handler: Optional handler for progress notifications
timeout: Optional timeout for requests (seconds or timedelta)
init_timeout: Optional timeout for initial connection (seconds or timedelta).
Set to 0 to disable. If None, uses the value in the FastMCP global settings.
Examples:
```python
# Connect to FastMCP server
client = Client("http://localhost:8080")
async with client:
# List available resources
resources = await client.list_resources()
# Call a tool
result = await client.call_tool("my_tool", {"param": "value"})
```
"""
@overload
def __init__(self: Client[T], transport: T, *args: Any, **kwargs: Any) -> None: ...
@overload
def __init__(
self: Client[SSETransport | StreamableHttpTransport],
transport: AnyUrl,
*args: Any,
**kwargs: Any,
) -> None: ...
@overload
def __init__(
self: Client[FastMCPTransport],
transport: FastMCP | FastMCP1Server,
*args: Any,
**kwargs: Any,
) -> None: ...
@overload
def __init__(
self: Client[PythonStdioTransport | NodeStdioTransport],
transport: Path,
*args: Any,
**kwargs: Any,
) -> None: ...
@overload
def __init__(
self: Client[MCPConfigTransport],
transport: MCPConfig | dict[str, Any],
*args: Any,
**kwargs: Any,
) -> None: ...
@overload
def __init__(
self: Client[
PythonStdioTransport
| NodeStdioTransport
| SSETransport
| StreamableHttpTransport
],
transport: str,
*args: Any,
**kwargs: Any,
) -> None: ...
def __init__(
self,
transport: (
ClientTransportT
| FastMCP
| FastMCP1Server
| AnyUrl
| Path
| MCPConfig
| dict[str, Any]
| str
),
name: str | None = None,
roots: RootsList | RootsHandler | None = None,
sampling_handler: ClientSamplingHandler | None = None,
elicitation_handler: ElicitationHandler | None = None,
log_handler: LogHandler | None = None,
message_handler: MessageHandlerT | MessageHandler | None = None,
progress_handler: ProgressHandler | None = None,
timeout: datetime.timedelta | float | int | None = None,
init_timeout: datetime.timedelta | float | int | None = None,
client_info: mcp.types.Implementation | None = None,
auth: httpx.Auth | Literal["oauth"] | str | None = None,
) -> None:
self.name = name or self.generate_name()
self.transport = cast(ClientTransportT, infer_transport(transport))
if auth is not None:
self.transport._set_auth(auth)
if log_handler is None:
log_handler = default_log_handler
if progress_handler is None:
progress_handler = default_progress_handler
self._progress_handler = progress_handler
if isinstance(timeout, int | float):
timeout = datetime.timedelta(seconds=float(timeout))
# handle init handshake timeout
if init_timeout is None:
init_timeout = fastmcp.settings.client_init_timeout
if isinstance(init_timeout, datetime.timedelta):
init_timeout = init_timeout.total_seconds()
elif not init_timeout:
init_timeout = None
else:
init_timeout = float(init_timeout)
self._init_timeout = init_timeout
self._session_kwargs: SessionKwargs = {
"sampling_callback": None,
"list_roots_callback": None,
"logging_callback": create_log_callback(log_handler),
"message_handler": message_handler,
"read_timeout_seconds": timeout,
"client_info": client_info,
}
if roots is not None:
self.set_roots(roots)
if sampling_handler is not None:
self._session_kwargs["sampling_callback"] = create_sampling_callback(
sampling_handler
)
if elicitation_handler is not None:
self._session_kwargs["elicitation_callback"] = create_elicitation_callback(
elicitation_handler
)
# Session context management - see class docstring for detailed explanation
self._session_state = ClientSessionState()
@property
def session(self) -> ClientSession:
"""Get the current active session. Raises RuntimeError if not connected."""
if self._session_state.session is None:
raise RuntimeError(
"Client is not connected. Use the 'async with client:' context manager first."
)
return self._session_state.session
@property
def initialize_result(self) -> mcp.types.InitializeResult:
"""Get the result of the initialization request."""
if self._session_state.initialize_result is None:
raise RuntimeError(
"Client is not connected. Use the 'async with client:' context manager first."
)
return self._session_state.initialize_result
def set_roots(self, roots: RootsList | RootsHandler) -> None:
"""Set the roots for the client. This does not automatically call `send_roots_list_changed`."""
self._session_kwargs["list_roots_callback"] = create_roots_callback(roots)
def set_sampling_callback(self, sampling_callback: ClientSamplingHandler) -> None:
"""Set the sampling callback for the client."""
self._session_kwargs["sampling_callback"] = create_sampling_callback(
sampling_callback
)
def set_elicitation_callback(
self, elicitation_callback: ElicitationHandler
) -> None:
"""Set the elicitation callback for the client."""
self._session_kwargs["elicitation_callback"] = create_elicitation_callback(
elicitation_callback
)
def is_connected(self) -> bool:
"""Check if the client is currently connected."""
return self._session_state.session is not None
def new(self) -> Client[ClientTransportT]:
"""Create a new client instance with the same configuration but fresh session state.
This creates a new client with the same transport, handlers, and configuration,
but with no active session. Useful for creating independent sessions that don't
share state with the original client.
Returns:
A new Client instance with the same configuration but disconnected state.
Example:
```python
# Create a fresh client for each concurrent operation
fresh_client = client.new()
async with fresh_client:
await fresh_client.call_tool("some_tool", {})
```
"""
new_client = copy.copy(self)
if not isinstance(self.transport, StdioTransport):
# Reset session state to fresh state
new_client._session_state = ClientSessionState()
new_client.name += f":{secrets.token_hex(2)}"
return new_client
@asynccontextmanager
async def _context_manager(self):
with catch(get_catch_handlers()):
async with self.transport.connect_session(
**self._session_kwargs
) as session:
self._session_state.session = session
# Initialize the session
try:
with anyio.fail_after(self._init_timeout):
self._session_state.initialize_result = (
await self._session_state.session.initialize()
)
yield
except anyio.ClosedResourceError as e:
raise RuntimeError("Server session was closed unexpectedly") from e
except TimeoutError as e:
raise RuntimeError("Failed to initialize server session") from e
finally:
self._session_state.session = None
self._session_state.initialize_result = None
async def __aenter__(self):
return await self._connect()
async def __aexit__(self, exc_type, exc_val, exc_tb):
await self._disconnect()
async def _connect(self):
"""
Establish or reuse a session connection.
This method implements the reentrant context manager pattern:
- First call: Creates background session task and waits for it to be ready
- Subsequent calls: Increments reference counter and reuses existing session
- All operations protected by _context_lock to prevent race conditions
The critical fix: Events are only created when starting a new session,
never reset outside the lock, preventing the deadlock scenario where
tasks wait on events that get replaced by other tasks.
"""
# ensure only one session is running at a time to avoid race conditions
async with self._session_state.lock:
need_to_start = (
self._session_state.session_task is None
or self._session_state.session_task.done()
)
if need_to_start:
if self._session_state.nesting_counter != 0:
raise RuntimeError(
f"Internal error: nesting counter should be 0 when starting new session, got {self._session_state.nesting_counter}"
)
self._session_state.stop_event = anyio.Event()
self._session_state.ready_event = anyio.Event()
self._session_state.session_task = asyncio.create_task(
self._session_runner()
)
await self._session_state.ready_event.wait()
if self._session_state.session_task.done():
exception = self._session_state.session_task.exception()
if exception is None:
raise RuntimeError(
"Session task completed without exception but connection failed"
)
if isinstance(exception, httpx.HTTPStatusError):
raise exception
raise RuntimeError(
f"Client failed to connect: {exception}"
) from exception
self._session_state.nesting_counter += 1
return self
async def _disconnect(self, force: bool = False):
"""
Disconnect from session using reference counting.
This method implements proper cleanup for reentrant context managers:
- Decrements reference counter for normal exits
- Only stops session when counter reaches 0 (no more active contexts)
- Force flag bypasses reference counting for immediate shutdown
- Session cleanup happens inside the lock to ensure atomicity
Key fix: Removed the problematic "Reset for future reconnects" logic
that was resetting events outside the lock, causing race conditions.
Event recreation now happens only in _connect() when actually needed.
"""
# ensure only one session is running at a time to avoid race conditions
async with self._session_state.lock:
# if we are forcing a disconnect, reset the nesting counter
if force:
self._session_state.nesting_counter = 0
# otherwise decrement to check if we are done nesting
else:
self._session_state.nesting_counter = max(
0, self._session_state.nesting_counter - 1
)
# if we are still nested, return
if self._session_state.nesting_counter > 0:
return
# stop the active session
if self._session_state.session_task is None:
return
self._session_state.stop_event.set()
# wait for session to finish to ensure state has been reset
await self._session_state.session_task
self._session_state.session_task = None
async def _session_runner(self):
"""
Background task that manages the actual session lifecycle.
This task runs in the background and:
1. Establishes the transport connection via _context_manager()
2. Signals that the session is ready via _ready_event.set()
3. Waits for disconnect signal via _stop_event.wait()
4. Ensures _ready_event is always set, even on failures
The simplified error handling (compared to the original) removes
redundant exception re-raising while ensuring waiting tasks are
always unblocked via the finally block.
"""
try:
async with AsyncExitStack() as stack:
await stack.enter_async_context(self._context_manager())
# Session/context is now ready
self._session_state.ready_event.set()
# Wait until disconnect/stop is requested
await self._session_state.stop_event.wait()
finally:
# Ensure ready event is set even if context manager entry fails
self._session_state.ready_event.set()
async def close(self):
await self._disconnect(force=True)
await self.transport.close()
# --- MCP Client Methods ---
async def ping(self) -> bool:
"""Send a ping request."""
result = await self.session.send_ping()
return isinstance(result, mcp.types.EmptyResult)
async def cancel(
self,
request_id: str | int,
reason: str | None = None,
) -> None:
"""Send a cancellation notification for an in-progress request."""
notification = mcp.types.ClientNotification(
root=mcp.types.CancelledNotification(
method="notifications/cancelled",
params=mcp.types.CancelledNotificationParams(
requestId=request_id,
reason=reason,
),
)
)
await self.session.send_notification(notification)
async def progress(
self,
progress_token: str | int,
progress: float,
total: float | None = None,
message: str | None = None,
) -> None:
"""Send a progress notification."""
await self.session.send_progress_notification(
progress_token, progress, total, message
)
async def set_logging_level(self, level: mcp.types.LoggingLevel) -> None:
"""Send a logging/setLevel request."""
await self.session.set_logging_level(level)
async def send_roots_list_changed(self) -> None:
"""Send a roots/list_changed notification."""
await self.session.send_roots_list_changed()
# --- Resources ---
async def list_resources_mcp(self) -> mcp.types.ListResourcesResult:
"""Send a resources/list request and return the complete MCP protocol result.
Returns:
mcp.types.ListResourcesResult: The complete response object from the protocol,
containing the list of resources and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called list_resources")
result = await self.session.list_resources()
return result
async def list_resources(self) -> list[mcp.types.Resource]:
"""Retrieve a list of resources available on the server.
Returns:
list[mcp.types.Resource]: A list of Resource objects.
Raises:
RuntimeError: If called while the client is not connected.
"""
result = await self.list_resources_mcp()
return result.resources
async def list_resource_templates_mcp(
self,
) -> mcp.types.ListResourceTemplatesResult:
"""Send a resources/listResourceTemplates request and return the complete MCP protocol result.
Returns:
mcp.types.ListResourceTemplatesResult: The complete response object from the protocol,
containing the list of resource templates and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called list_resource_templates")
result = await self.session.list_resource_templates()
return result
async def list_resource_templates(
self,
) -> list[mcp.types.ResourceTemplate]:
"""Retrieve a list of resource templates available on the server.
Returns:
list[mcp.types.ResourceTemplate]: A list of ResourceTemplate objects.
Raises:
RuntimeError: If called while the client is not connected.
"""
result = await self.list_resource_templates_mcp()
return result.resourceTemplates
async def read_resource_mcp(
self, uri: AnyUrl | str
) -> mcp.types.ReadResourceResult:
"""Send a resources/read request and return the complete MCP protocol result.
Args:
uri (AnyUrl | str): The URI of the resource to read. Can be a string or an AnyUrl object.
Returns:
mcp.types.ReadResourceResult: The complete response object from the protocol,
containing the resource contents and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called read_resource: {uri}")
if isinstance(uri, str):
uri = AnyUrl(uri) # Ensure AnyUrl
result = await self.session.read_resource(uri)
return result
async def read_resource(
self, uri: AnyUrl | str
) -> list[mcp.types.TextResourceContents | mcp.types.BlobResourceContents]:
"""Read the contents of a resource or resolved template.
Args:
uri (AnyUrl | str): The URI of the resource to read. Can be a string or an AnyUrl object.
Returns:
list[mcp.types.TextResourceContents | mcp.types.BlobResourceContents]: A list of content
objects, typically containing either text or binary data.
Raises:
RuntimeError: If called while the client is not connected.
"""
if isinstance(uri, str):
try:
uri = AnyUrl(uri) # Ensure AnyUrl
except Exception as e:
raise ValueError(
f"Provided resource URI is invalid: {str(uri)!r}"
) from e
result = await self.read_resource_mcp(uri)
return result.contents
# async def subscribe_resource(self, uri: AnyUrl | str) -> None:
# """Send a resources/subscribe request."""
# if isinstance(uri, str):
# uri = AnyUrl(uri)
# await self.session.subscribe_resource(uri)
# async def unsubscribe_resource(self, uri: AnyUrl | str) -> None:
# """Send a resources/unsubscribe request."""
# if isinstance(uri, str):
# uri = AnyUrl(uri)
# await self.session.unsubscribe_resource(uri)
# --- Prompts ---
async def list_prompts_mcp(self) -> mcp.types.ListPromptsResult:
"""Send a prompts/list request and return the complete MCP protocol result.
Returns:
mcp.types.ListPromptsResult: The complete response object from the protocol,
containing the list of prompts and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called list_prompts")
result = await self.session.list_prompts()
return result
async def list_prompts(self) -> list[mcp.types.Prompt]:
"""Retrieve a list of prompts available on the server.
Returns:
list[mcp.types.Prompt]: A list of Prompt objects.
Raises:
RuntimeError: If called while the client is not connected.
"""
result = await self.list_prompts_mcp()
return result.prompts
# --- Prompt ---
async def get_prompt_mcp(
self, name: str, arguments: dict[str, Any] | None = None
) -> mcp.types.GetPromptResult:
"""Send a prompts/get request and return the complete MCP protocol result.
Args:
name (str): The name of the prompt to retrieve.
arguments (dict[str, Any] | None, optional): Arguments to pass to the prompt. Defaults to None.
Returns:
mcp.types.GetPromptResult: The complete response object from the protocol,
containing the prompt messages and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called get_prompt: {name}")
# Serialize arguments for MCP protocol - convert non-string values to JSON
serialized_arguments: dict[str, str] | None = None
if arguments:
serialized_arguments = {}
for key, value in arguments.items():
if isinstance(value, str):
serialized_arguments[key] = value
else:
# Use pydantic_core.to_json for consistent serialization
serialized_arguments[key] = pydantic_core.to_json(value).decode(
"utf-8"
)
result = await self.session.get_prompt(
name=name, arguments=serialized_arguments
)
return result
async def get_prompt(
self, name: str, arguments: dict[str, Any] | None = None
) -> mcp.types.GetPromptResult:
"""Retrieve a rendered prompt message list from the server.
Args:
name (str): The name of the prompt to retrieve.
arguments (dict[str, Any] | None, optional): Arguments to pass to the prompt. Defaults to None.
Returns:
mcp.types.GetPromptResult: The complete response object from the protocol,
containing the prompt messages and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
result = await self.get_prompt_mcp(name=name, arguments=arguments)
return result
# --- Completion ---
async def complete_mcp(
self,
ref: mcp.types.ResourceTemplateReference | mcp.types.PromptReference,
argument: dict[str, str],
context_arguments: dict[str, Any] | None = None,
) -> mcp.types.CompleteResult:
"""Send a completion request and return the complete MCP protocol result.
Args:
ref (mcp.types.ResourceTemplateReference | mcp.types.PromptReference): The reference to complete.
argument (dict[str, str]): Arguments to pass to the completion request.
context_arguments (dict[str, Any] | None, optional): Optional context arguments to
include with the completion request. Defaults to None.
Returns:
mcp.types.CompleteResult: The complete response object from the protocol,
containing the completion and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called complete: {ref}")
result = await self.session.complete(
ref=ref, argument=argument, context_arguments=context_arguments
)
return result
async def complete(
self,
ref: mcp.types.ResourceTemplateReference | mcp.types.PromptReference,
argument: dict[str, str],
context_arguments: dict[str, Any] | None = None,
) -> mcp.types.Completion:
"""Send a completion request to the server.
Args:
ref (mcp.types.ResourceTemplateReference | mcp.types.PromptReference): The reference to complete.
argument (dict[str, str]): Arguments to pass to the completion request.
context_arguments (dict[str, Any] | None, optional): Optional context arguments to
include with the completion request. Defaults to None.
Returns:
mcp.types.Completion: The completion object.
Raises:
RuntimeError: If called while the client is not connected.
"""
result = await self.complete_mcp(
ref=ref, argument=argument, context_arguments=context_arguments
)
return result.completion
# --- Tools ---
async def list_tools_mcp(self) -> mcp.types.ListToolsResult:
"""Send a tools/list request and return the complete MCP protocol result.
Returns:
mcp.types.ListToolsResult: The complete response object from the protocol,
containing the list of tools and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called list_tools")
result = await self.session.list_tools()
return result
async def list_tools(self) -> list[mcp.types.Tool]:
"""Retrieve a list of tools available on the server.
Returns:
list[mcp.types.Tool]: A list of Tool objects.
Raises:
RuntimeError: If called while the client is not connected.
"""
result = await self.list_tools_mcp()
return result.tools
# --- Call Tool ---
async def call_tool_mcp(
self,
name: str,
arguments: dict[str, Any],
progress_handler: ProgressHandler | None = None,
timeout: datetime.timedelta | float | int | None = None,
) -> mcp.types.CallToolResult:
"""Send a tools/call request and return the complete MCP protocol result.
This method returns the raw CallToolResult object, which includes an isError flag
and other metadata. It does not raise an exception if the tool call results in an error.
Args:
name (str): The name of the tool to call.
arguments (dict[str, Any]): Arguments to pass to the tool.
timeout (datetime.timedelta | float | int | None, optional): The timeout for the tool call. Defaults to None.
progress_handler (ProgressHandler | None, optional): The progress handler to use for the tool call. Defaults to None.
Returns:
mcp.types.CallToolResult: The complete response object from the protocol,
containing the tool result and any additional metadata.
Raises:
RuntimeError: If called while the client is not connected.
"""
logger.debug(f"[{self.name}] called call_tool: {name}")
if isinstance(timeout, int | float):
timeout = datetime.timedelta(seconds=float(timeout))
result = await self.session.call_tool(
name=name,
arguments=arguments,
read_timeout_seconds=timeout,
progress_callback=progress_handler or self._progress_handler,
)
return result
async def call_tool(
self,
name: str,
arguments: dict[str, Any] | None = None,
timeout: datetime.timedelta | float | int | None = None,
progress_handler: ProgressHandler | None = None,
raise_on_error: bool = True,
) -> CallToolResult:
"""Call a tool on the server.
Unlike call_tool_mcp, this method raises a ToolError if the tool call results in an error.
Args:
name (str): The name of the tool to call.
arguments (dict[str, Any] | None, optional): Arguments to pass to the tool. Defaults to None.
timeout (datetime.timedelta | float | int | None, optional): The timeout for the tool call. Defaults to None.
progress_handler (ProgressHandler | None, optional): The progress handler to use for the tool call. Defaults to None.
Returns:
CallToolResult:
The content returned by the tool. If the tool returns structured
outputs, they are returned as a dataclass (if an output schema
is available) or a dictionary; otherwise, a list of content
blocks is returned. Note: to receive both structured and
unstructured outputs, use call_tool_mcp instead and access the
raw result object.
Raises:
ToolError: If the tool call results in an error.
RuntimeError: If called while the client is not connected.
"""
result = await self.call_tool_mcp(
name=name,
arguments=arguments or {},
timeout=timeout,
progress_handler=progress_handler,
)
data = None
if result.isError and raise_on_error:
msg = cast(mcp.types.TextContent, result.content[0]).text
raise ToolError(msg)
elif result.structuredContent:
try:
if name not in self.session._tool_output_schemas:
await self.session.list_tools()
if name in self.session._tool_output_schemas:
output_schema = self.session._tool_output_schemas.get(name)
if output_schema:
if output_schema.get("x-fastmcp-wrap-result"):
output_schema = output_schema.get("properties", {}).get(
"result"
)
structured_content = result.structuredContent.get("result")
else:
structured_content = result.structuredContent
output_type = json_schema_to_type(output_schema)
type_adapter = get_cached_typeadapter(output_type)
data = type_adapter.validate_python(structured_content)
else:
data = result.structuredContent
except Exception as e:
logger.error(f"[{self.name}] Error parsing structured content: {e}")
return CallToolResult(
content=result.content,
structured_content=result.structuredContent,
data=data,
is_error=result.isError,
)
@classmethod
def generate_name(cls, name: str | None = None) -> str:
class_name = cls.__name__
if name is None:
return f"{class_name}-{secrets.token_hex(2)}"
else:
return f"{class_name}-{name}-{secrets.token_hex(2)}"
@dataclass
class CallToolResult:
content: list[mcp.types.ContentBlock]
structured_content: dict[str, Any] | None
data: Any = None
is_error: bool = False
|