Update MCP tool call customisation docs (#2817)

Signed-off-by: Matthew Peveler <[email protected]>
Co-authored-by: Douwe Maan <[email protected]>

Author: MasterOdin

docs/mcp/client.md

@@ -222,7 +222,7 @@ The MCP servers provide the ability to set a `process_tool_call` which allows
 the customisation of tool call requests and their responses.
 
 A common use case for this is to inject metadata to the requests which the server
-call needs.
+call needs:
 
 ```python {title="mcp_process_tool_call.py"}
 from typing import Any
@@ -257,6 +257,40 @@ async def main():
     #> {"echo_deps":{"echo":"This is an echo message","deps":42}}
 ```
 
+How to access the metadata is MCP server SDK specific. For example with the [MCP Python
+SDK](https://github.com/modelcontextprotocol/python-sdk), it is accessible via the
+[`ctx: Context`](https://github.com/modelcontextprotocol/python-sdk#context)
+argument that can be included on tool call handlers:
+
+```python {title="mcp_server.py"}
+from typing import Any
+
+from mcp.server.fastmcp import Context, FastMCP
+from mcp.server.session import ServerSession
+
+mcp = FastMCP('Pydantic AI MCP Server')
+log_level = 'unset'
+
+
+@mcp.tool()
+async def echo_deps(ctx: Context[ServerSession, None]) -> dict[str, Any]:
+    """Echo the run context.
+
+    Args:
+        ctx: Context object containing request and session information.
+
+    Returns:
+        Dictionary with an echo message and the deps.
+    """
+    await ctx.info('This is an info message')
+
+    deps: Any = getattr(ctx.request_context.meta, 'deps')
+    return {'echo': 'This is an echo message', 'deps': deps}
+
+if __name__ == '__main__':
+    mcp.run()
+```
+
 ## Using Tool Prefixes to Avoid Naming Conflicts
 
 When connecting to multiple MCP servers that might provide tools with the same name, you can use the `tool_prefix` parameter to avoid naming conflicts. This parameter adds a prefix to all tool names from a specific server.