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510 | class MCPClient:
"""FastMCP-based client for communicating with MCP servers."""
def __init__(
self,
elicitation_callback: ElicitationHandler | None = None,
sampling_callback: ClientSamplingHandler | None = None,
progress_handler: ContextualProgressHandler | None = None,
message_handler: MessageHandlerT | MessageHandler | None = None,
accessible_roots: list[str] | None = None,
):
self._elicitation_callback = elicitation_callback
self._sampling_callback = sampling_callback
self._progress_handler = MultiEventHandler[ContextualProgressHandler](
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._client: fastmcp.Client | None = None
self._available_tools: list[MCPTool] = []
self._connected = False
async def __aenter__(self) -> Self:
"""Enter context manager."""
return self
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
):
"""Exit context manager and cleanup."""
await self.cleanup()
async def cleanup(self):
"""Clean up resources."""
if self._client:
try:
await self._client.__aexit__(None, None, None)
except Exception as e: # noqa: BLE001
logger.warning("Error during FastMCP client cleanup: %s", e)
finally:
self._client = None
self._connected = False
self._available_tools = []
async def _log_handler(self, message: LogMessage) -> None:
"""Handle server log messages."""
msg = message.data.get("msg", "")
level = LEVEL_MAP.get(message.level.lower(), logging.INFO)
logger.log(level, "MCP Server: %s", msg)
async def _elicitation_handler_impl(
self,
message: str,
response_type: type,
params: ElicitRequestParams,
context: RequestContext,
) -> ElicitResult[dict[str, Any]] | dict[str, Any] | None:
"""Handle elicitation requests from server."""
if not self._elicitation_callback:
return None
try:
# Direct FastMCP callback - no compatibility layer
return await self._elicitation_callback(
message, response_type, params, context
)
except Exception:
logger.exception("Elicitation handler failed")
from fastmcp.client.elicitation import ElicitResult
return ElicitResult(action="cancel")
async def _sampling_handler_impl(
self,
messages: list[SamplingMessage],
params: CreateMessageRequestParams,
context: RequestContext,
) -> str:
"""Handle sampling requests from server."""
if not self._sampling_callback:
return "Sampling not supported"
try:
result = self._sampling_callback(messages, params, context)
if inspect.iscoroutine(result):
result = await result
return str(result)
except Exception as e:
logger.exception("Sampling handler failed")
return f"Sampling failed: {e}"
async def connect(self, config: MCPServerConfig):
"""Connect to an MCP server using FastMCP.
Args:
config: MCP server configuration object
"""
try:
# First attempt with configured auth
self._client = self._get_client(config)
await self._client.__aenter__()
except Exception as first_error:
# OAuth fallback for HTTP/SSE if not already using OAuth
if _should_try_oauth_fallback(config):
try:
if self._client:
with contextlib.suppress(Exception):
await self._client.__aexit__(None, None, None)
self._client = self._get_client(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
self._connected = True
await self._refresh_tools()
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
from llmling_agent_config.mcp_server import (
SSEMCPServerConfig,
StdioMCPServerConfig,
StreamableHTTPMCPServerConfig,
)
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: MessageHandlerT | MessageHandler | None
if not self._message_handler:
from llmling_agent.mcp_server.message_handler import MCPMessageHandler
msg_handler = MCPMessageHandler(self)
else:
msg_handler = self._message_handler
return fastmcp.Client(
transport,
log_handler=self._log_handler,
roots=self._accessible_roots,
timeout=config.timeout,
elicitation_handler=self._elicitation_handler_impl,
sampling_handler=self._sampling_handler_impl,
message_handler=msg_handler,
auth="oauth" if (force_oauth or oauth) else None,
)
async def _refresh_tools(self) -> None:
"""Refresh the list of available tools from the server."""
if not self._client or not self._connected:
return
try:
tools = await self._client.list_tools()
self._available_tools = tools
logger.debug("Refreshed %d tools from MCP server", len(tools))
except Exception as e: # noqa: BLE001
logger.warning("Failed to refresh tools: %s", e)
self._available_tools = []
def get_tools(self) -> list[dict[str, Any]]:
"""Get tools in OpenAI function format."""
return [
{"type": "function", "function": mcp_tool_to_fn_schema(tool)}
for tool in self._available_tools
]
async def list_prompts(self) -> list[MCPPrompt]:
"""Get available prompts from the server."""
if not self._client or not self._connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
try:
return await self._client.list_prompts()
except Exception as e:
msg = f"Failed to list prompts: {e}"
raise RuntimeError(msg) from e
async def list_resources(self) -> list[MCPResource]:
"""Get available resources from the server."""
if not self._client or 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
) -> mcp.types.GetPromptResult:
"""Get a specific prompt's content."""
if not self._client or 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."""
from llmling_agent import Tool
schema = mcp_tool_to_fn_schema(tool)
fn_schema = FunctionSchema.from_dict(schema)
sig = fn_schema.to_python_signature()
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)
}
tc_id = ctx.tool_call_id if ctx else None
return await self.call_tool(
tool.name,
filtered_kwargs,
tool_call_id=tc_id,
run_context=ctx,
)
# Set proper signature and annotations with RunContext support
tool_callable.__signature__ = _create_tool_signature_with_context(sig) # type: ignore
annotations = _create_tool_annotations_with_context(fn_schema.get_annotations())
# Update return annotation to support multiple types
annotations["return"] = str | Any | ToolReturn
tool_callable.__annotations__ = annotations
tool_callable.__name__ = tool.name
tool_callable.__doc__ = tool.description or "No description provided."
meta = {"mcp_tool": tool.name}
return Tool.from_callable(tool_callable, source="mcp", metadata=meta)
def _create_progress_handler_with_context(
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,
arguments: dict | None = None,
tool_call_id: str | None = None,
run_context: RunContext | None = None,
) -> ToolReturn | str | Any:
"""Call an MCP tool with full PydanticAI return type support."""
if not self._client or not self._connected:
msg = "Not connected to MCP server"
raise RuntimeError(msg)
try:
# Create progress handler if we have handler
progress_handler = None
if self._progress_handler:
if run_context and 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_progress_handler_with_context(
run_context.tool_name, run_context.tool_call_id, tool_input
)
else:
# Fallback to using passed arguments (direct tool call)
progress_handler = self._create_progress_handler_with_context(
name, tool_call_id or "", arguments or {}
)
# Use FastMCP's call_tool method with optional progress handler
result = await self._client.call_tool(
name, arguments, progress_handler=progress_handler
)
# Convert MCP content to PydanticAI content
pydantic_content = await self._convert_mcp_content_to_pydantic(result.content)
# Decision logic for return type
match (result.data is not None, bool(pydantic_content)):
case (True, True):
# Both structured data and rich content -> ToolReturn
return ToolReturn(return_value=result.data, content=pydantic_content)
case (True, False):
# Only structured data -> return directly
return result.data
case (False, True):
# Only content -> ToolReturn with content
return ToolReturn(
return_value="Tool executed successfully",
content=pydantic_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_to_pydantic(
self, mcp_content: list[Any]
) -> list[str | Any]:
"""Convert MCP content blocks to PydanticAI content types."""
from mcp.types import (
AudioContent,
BlobResourceContents,
EmbeddedResource,
ImageContent,
ResourceLink,
TextContent,
TextResourceContents,
)
pydantic_content: list[Any] = []
for block in mcp_content:
match block:
case TextContent(text=text):
pydantic_content.append(text)
case TextResourceContents(text=text):
pydantic_content.append(text)
case ImageContent(data=data, mimeType=mime_type):
# MCP data can be either bytes or base64 encoded string
decoded_data = base64.b64decode(data)
img = BinaryImage(data=decoded_data, media_type=mime_type)
pydantic_content.append(img)
case AudioContent(data=data, mimeType=mime_type):
# MCP data can be either bytes or base64 encoded string
decoded_data = base64.b64decode(data)
content = BinaryContent(data=decoded_data, media_type=mime_type)
pydantic_content.append(content)
case BlobResourceContents(blob=blob):
# MCP blob can be either bytes or base64 encoded string
decoded_data = base64.b64decode(blob)
mime = "application/octet-stream"
content = BinaryContent(data=decoded_data, media_type=mime)
pydantic_content.append(content)
case ResourceLink(uri=uri):
# ResourceContentBlock should be read like PydanticAI does
try:
assert self._client
resource_result = await self._client.read_resource_mcp(uri)
if len(resource_result.contents) == 1:
nested_result = await self._convert_mcp_content_to_pydantic([
resource_result.contents[0]
])
pydantic_content.extend(nested_result)
else:
nested_result = await self._convert_mcp_content_to_pydantic(
resource_result.contents
)
pydantic_content.extend(nested_result)
except Exception: # noqa: BLE001
# Fallback to DocumentUrl if reading fails
pydantic_content.append(DocumentUrl(url=str(uri)))
case EmbeddedResource(resource=TextResourceContents(text=text)):
pydantic_content.append(text)
case EmbeddedResource(resource=BlobResourceContents() as blob_resource):
pydantic_content.append(f"[Binary data: {blob_resource.mimeType}]")
case _:
# Convert anything else to string
pydantic_content.append(str(block))
return pydantic_content
|