Progress Monitoring

Handle progress notifications from long-running server operations.

New in version 2.3.5

Use this when you need to track progress of long-running operations.

MCP servers can report progress during operations. The client receives these updates through a progress handler.

Progress Handler

Set a handler when creating the client:

from fastmcp import Client

async def progress_handler(
    progress: float,
    total: float | None,
    message: str | None
) -> None:
    if total is not None:
        percentage = (progress / total) * 100
        print(f"Progress: {percentage:.1f}% - {message or ''}")
    else:
        print(f"Progress: {progress} - {message or ''}")

client = Client(
    "my_mcp_server.py",
    progress_handler=progress_handler
)

The handler receives three parameters:

Handler Parameters

progress · float

Current progress value

total · float | None

Expected total value (may be None if unknown)

message · str | None

Optional status message

Per-Call Handler

Override the client-level handler for specific tool calls:

async with client:
    result = await client.call_tool(
        "long_running_task",
        {"param": "value"},
        progress_handler=my_progress_handler
    )