How to get session_id in tool

[bhxiaoxinba]

in the function of @mcp.tool , i want to get session_id, how i can get it?

[ghostidentity]

Im having the same issue also, i can see the session_id is being passed

[shiwenbin1617]

mark

[NICK-DUAN]

+1

[CrossNox]

from mcp.server.fastmcp import Context, FastMCP

...

def _get_session_id(ctx: Context) -> int:
    """Get a unique session from the context."""
    return id(ctx.session)

...

@mcp.tool()
async def your_tool(ctx: Context = None):
    """Some cool description"""
    session_id = _get_session_id(ctx)
    ...

[amir-arad]

def get_session_id(ctx: Context) -> str:
    """
    Get a consistent session ID from an MCP context regardless of transport.
    
    Args:
        ctx: The MCP context object
        
    Returns:
        A unique session identifier that persists for the duration of the session
    """
    if not ctx or not hasattr(ctx, 'session') or not ctx.session:
        raise ValueError("Invalid context - missing session")
        
    session = ctx.session
    
    # Check if we already assigned a session ID
    internal_attr_name = '__session_id'
    if hasattr(session, internal_attr_name):
        return getattr(session, internal_attr_name)
    
    session_id = f"s_{id(session):x}_{random.randint(0, 255):02x}"
    
    setattr(session, internal_attr_name, session_id)
        
    return session_id

[maxisbey]

Now tracked in #2098.