Fix #892 by adding proper tool description in context.md

[Abbas-Asad]

Summary

This pull request fixes issue #892 by adding a missing docstring to the fetch_user_age tool function in docs/context.md.

Problem

Many non-OpenAI LLMs (such as Claude, Gemini, Mistral, etc.) are unable to use the fetch_user_age function because it lacks a docstring. As a result, they return responses like:

"I cannot determine the user's age because the available tools lack the ability to fetch user-specific information."

Changes Made

• Added a one-line docstring to the fetch_user_age function
• Improved return statement to match expected tool output

@function_tool
async def fetch_user_age(wrapper: RunContextWrapper[UserInfo]) -> str:
    """Fetch the age of the user. Call this function to get user's age information."""
    return f"The user {wrapper.context.name} is 47 years old"