progress_token is 0 on first tool-call and the return is taken mistakenly

[sheffler]

The first time a tool is called the progress_token is present, but its value is 0. The way the conditional
is written the value of 0 is False and (not 0) is True. What we want is to return if the value is not present (None).

Motivation and Context

I had a small server that sent progress notifications and I noticed that on the first call to the tool, the
progress notifications were not sent. On subsequent tool calls they were.

How Has This Been Tested?

Yes. I have tested with a small server and observed the progress notifications in Inspector.

Breaking Changes

No

Types of changes

• [x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• [x ] I have read the MCP Documentation
• [ x] My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

See console output of request sent on first call of tool. The value of progressToken in the _meta is 0. Thus
it is present.

[sheffler]

Simple test server for exercising progress reporting.

# FAST MCP server

from mcp.server.fastmcp import FastMCP, Context
import time

#
# LOGGER
#

import logging
logger = logging.getLogger('tom2')
logger.setLevel(logging.DEBUG)
logger.debug("Starting TOm2 Server")

mcp = FastMCP("Tom2 Server 2024-01-23", debug=True, log_level="INFO")


@mcp.resource("config://app")
def get_config() -> str:
    """Static configuration data"""
    return "Tom2 Server 2024-01-23"

@mcp.tool()
async def my_tool(x: float, y:float, ctx:Context) -> str:
    """Perform a long running calculation"""

    await ctx.info(f"Processing 1")
    await ctx.report_progress(1, 2)
    await ctx.debug(f"Processing 2")
    await ctx.request_context.session.send_log_message("debug", "Explicit Processing 3")
    await ctx.report_progress(2, 2)
    return x*y

[sheffler]

This looks better than my suggestion. Thank you.
(P.S. - i sent you a note on Linked In about MCP)

[tanhaipeng]

Simple test server for exercising progress reporting.用于练习进度报告的简单测试服务器。

# FAST MCP server

from mcp.server.fastmcp import FastMCP, Context
import time

#
# LOGGER
#

import logging
logger = logging.getLogger('tom2')
logger.setLevel(logging.DEBUG)
logger.debug("Starting TOm2 Server")

mcp = FastMCP("Tom2 Server 2024-01-23", debug=True, log_level="INFO")


@mcp.resource("config://app")
def get_config() -> str:
    """Static configuration data"""
    return "Tom2 Server 2024-01-23"

@mcp.tool()
async def my_tool(x: float, y:float, ctx:Context) -> str:
    """Perform a long running calculation"""

    await ctx.info(f"Processing 1")
    await ctx.report_progress(1, 2)
    await ctx.debug(f"Processing 2")
    await ctx.request_context.session.send_log_message("debug", "Explicit Processing 3")
    await ctx.report_progress(2, 2)
    return x*y

How does the client receive progress notifications from the server?