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341 | class MCPClient:
"""FastMCP-based client for communicating with MCP servers."""
def __init__(
self,
config: MCPServerConfig,
elicitation_callback: ElicitationHandler | None = None,
sampling_callback: ClientSamplingHandler | None = None,
progress_handler: RichProgressCallback | None = None,
message_handler: MessageHandlerT | MessageHandler | None = None,
accessible_roots: list[str] | None = None,
tool_change_callback: Callable[[], Awaitable[None]] | None = None,
prompt_change_callback: Callable[[], Awaitable[None]] | None = None,
resource_change_callback: Callable[[], Awaitable[None]] | None = None,
):
self._elicitation_callback = elicitation_callback
self.config = config
self._sampling_callback = sampling_callback
self._progress_handler = MultiEventHandler[RichProgressCallback](
handlers=[progress_handler] if progress_handler else []
)
# Store message handler or mark for lazy creation
self._message_handler = message_handler
self._accessible_roots = accessible_roots or []
self._tool_change_callback = tool_change_callback
self._prompt_change_callback = prompt_change_callback
self._resource_change_callback = resource_change_callback
self._client = self._get_client(self.config)
@property
def connected(self) -> bool:
"""Check if client is connected by examining session state."""
return self._client.is_connected()
async def __aenter__(self) -> Self:
"""Enter context manager."""
try:
# First attempt with configured auth
await self._client.__aenter__()
except Exception as first_error:
# OAuth fallback for HTTP/SSE if not already using OAuth
if (
not isinstance(self.config, StdioMCPServerConfig)
and not self.config.auth.oauth
):
try:
with contextlib.suppress(Exception):
await self._client.__aexit__(None, None, None)
self._client = self._get_client(self.config, force_oauth=True)
await self._client.__aenter__()
logger.info("Connected with OAuth fallback")
except Exception: # noqa: BLE001
raise first_error from None
else:
raise
return self
async def __aexit__(self, *args: object):
"""Exit context manager and cleanup."""
try:
await self._client.__aexit__(None, None, None)
except Exception as e: # noqa: BLE001
logger.warning("Error during FastMCP client cleanup", error=e)
def get_resource_fs(self):
"""Get a filesystem for accessing MCP resources."""
from upathtools.filesystems.mcp_fs import MCPFileSystem
return MCPFileSystem(client=self._client)
async def _log_handler(self, message: LogMessage) -> None:
"""Handle server log messages."""
level = MCP_TO_LOGGING.get(message.level, logging.INFO)
logger.log(level, "MCP Server: ", data=message.data)
def _get_client(self, config: MCPServerConfig, force_oauth: bool = False):
"""Create FastMCP client based on config."""
import fastmcp
from fastmcp.client import SSETransport, StreamableHttpTransport
from fastmcp.client.transports import StdioTransport
transport: ClientTransport
# Create transport based on config type
match config:
case StdioMCPServerConfig(command=command, args=args):
env = config.get_env_vars()
transport = StdioTransport(command=command, args=args, env=env)
oauth = False
if force_oauth:
msg = "OAuth is not supported for StdioMCPServerConfig"
raise ValueError(msg)
case SSEMCPServerConfig(url=url, headers=headers, auth=auth):
transport = SSETransport(url=url, headers=headers)
oauth = auth.oauth
case StreamableHTTPMCPServerConfig(url=url, headers=headers, auth=auth):
transport = StreamableHttpTransport(url=url, headers=headers)
oauth = auth.oauth
case _:
msg = f"Unsupported server config type: {type(config)}"
raise ValueError(msg)
# Create message handler if needed
msg_handler = self._message_handler or MCPMessageHandler(
self,
self._tool_change_callback,
self._prompt_change_callback,
self._resource_change_callback,
)
return fastmcp.Client(
transport,
log_handler=self._log_handler,
roots=self._accessible_roots,
timeout=config.timeout,
elicitation_handler=self._elicitation_callback,
sampling_handler=self._sampling_callback,
message_handler=msg_handler,
auth="oauth" if (force_oauth or oauth) else None,
)
async def list_tools(self) -> list[MCPTool]:
"""Get available tools directly from the server."""
if not self.connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
try:
tools = await self._client.list_tools()
logger.debug("Listed tools from MCP server", num_tools=len(tools))
except Exception as e: # noqa: BLE001
logger.warning("Failed to list tools", error=e)
return []
else:
return tools
async def list_prompts(self) -> list[MCPPrompt]:
"""Get available prompts from the server."""
if not self.connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
try:
return await self._client.list_prompts()
except Exception as e: # noqa: BLE001
logger.debug("Failed to list prompts", error=e)
return []
async def list_resources(self) -> list[MCPResource]:
"""Get available resources from the server."""
if not self.connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
try:
return await self._client.list_resources()
except Exception as e:
msg = f"Failed to list resources: {e}"
raise RuntimeError(msg) from e
async def get_prompt(
self, name: str, arguments: dict[str, str] | None = None
) -> GetPromptResult:
"""Get a specific prompt's content."""
if not self.connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
try:
return await self._client.get_prompt_mcp(name, arguments)
except Exception as e:
msg = f"Failed to get prompt {name!r}: {e}"
raise RuntimeError(msg) from e
def convert_tool(self, tool: MCPTool) -> Tool:
"""Create a properly typed callable from MCP tool schema."""
async def tool_callable(ctx: RunContext, **kwargs: Any) -> str | Any | ToolReturn:
"""Dynamically generated MCP tool wrapper."""
# Filter out None values for optional params
schema_props = tool.inputSchema.get("properties", {})
required_props = set(tool.inputSchema.get("required", []))
filtered_kwargs = {
k: v
for k, v in kwargs.items()
if k in required_props or (k in schema_props and v is not None)
}
return await self.call_tool(tool.name, ctx, filtered_kwargs)
# Set proper signature and annotations with RunContext support
schema = mcp_tool_to_fn_schema(tool)
fn_schema = FunctionSchema.from_dict(schema)
sig = fn_schema.to_python_signature()
tool_callable.__signature__ = _create_tool_signature_with_context(sig) # type: ignore
annotations = fn_schema.get_annotations()
annotations["ctx"] = RunContext
# Update return annotation to support multiple types
annotations["return"] = str | Any | ToolReturn # type: ignore
tool_callable.__annotations__ = annotations
tool_callable.__name__ = tool.name
tool_callable.__doc__ = tool.description or "No description provided."
return Tool.from_callable(tool_callable, source="mcp")
def _create_final_progress_handler(
self, tool_name: str, tool_call_id: str, tool_input: dict[str, Any]
) -> ProgressHandler:
"""Create a FastMCP-compatible progress handler with baked-in context."""
async def fastmcp_progress_handler(
progress: float, total: float | None, message: str | None
):
await self._progress_handler(
progress, total, message, tool_name, tool_call_id, tool_input
)
return fastmcp_progress_handler
async def call_tool(
self,
name: str,
run_context: RunContext,
arguments: dict[str, Any] | None = None,
) -> ToolReturn | str | Any:
"""Call an MCP tool with full PydanticAI return type support."""
if not self.connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
# Create progress handler if we have handler
progress_handler = None
if self._progress_handler:
if run_context.tool_call_id and run_context.tool_name:
# Extract tool args from message history
tool_input = extract_tool_call_args(
run_context.messages, run_context.tool_call_id
)
progress_handler = self._create_final_progress_handler(
run_context.tool_name, run_context.tool_call_id, tool_input
)
else:
# Fallback to using passed arguments (direct tool call)
progress_handler = self._create_final_progress_handler(
name, run_context.tool_call_id or "", arguments or {}
)
try:
result = await self._client.call_tool(
name, arguments, progress_handler=progress_handler
)
content = await self._convert_mcp_content(result.content)
# Decision logic for return type
match (result.data is not None, bool(content)):
case (True, True): # Both structured data and rich content -> ToolReturn
return ToolReturn(return_value=result.data, content=content)
case (True, False): # Only structured data -> return directly
return result.data
case (False, True): # Only content -> ToolReturn with content
msg = "Tool executed successfully"
return ToolReturn(return_value=msg, content=content)
case (False, False): # Fallback to text extraction
return extract_text_content(result.content)
case _: # Handle unexpected cases
msg = f"Unexpected MCP content: {result.content}"
raise ValueError(msg) # noqa: TRY301
except Exception as e:
msg = f"MCP tool call failed: {e}"
raise RuntimeError(msg) from e
async def _convert_mcp_content(
self,
mcp_content: Sequence[ContentBlock | TextResourceContents | BlobResourceContents],
) -> list[str | BinaryContent]:
"""Convert MCP content blocks to PydanticAI content types."""
from llmling_agent.mcp_server.conversions import convert_mcp_content
return await convert_mcp_content(mcp_content)
|