Add instructions to the test server; tooltip to instructions example

Author: Motta Kin

docs/mcp/client.md

@@ -351,14 +351,16 @@ agent = Agent('openai:gpt-5', toolsets=[server])
 
 @agent.instructions
 async def mcp_server_instructions():
-    return server.instructions
+    return server.instructions  # (1)!
 
 async def main():
     result = await agent.run('What is 7 plus 5?')
     print(result.output)
     #> The answer is 12.
 ```
 
+1. The server connection is guaranteed to be established by this point, so `server.instructions` is available.
+
 ## Tool metadata
 
 MCP tools can include metadata that provides additional information about the tool's characteristics, which can be useful when [filtering tools][pydantic_ai.toolsets.FilteredToolset]. The `meta`, `annotations`, and `output_schema` fields can be found on the `metadata` dict on the [`ToolDefinition`][pydantic_ai.tools.ToolDefinition] object that's passed to filter functions.

tests/mcp_server.py

@@ -16,7 +16,7 @@
 )
 from pydantic import AnyUrl, BaseModel
 
-mcp = FastMCP('Pydantic AI MCP Server')
+mcp = FastMCP('Pydantic AI MCP Server', instructions='Be a helpful assistant.')
 log_level = 'unset'
 
 

tests/test_mcp.py

@@ -1764,7 +1764,7 @@ async def test_instructions(mcp_server: MCPServerStdio) -> None:
         mcp_server.instructions
     async with mcp_server:
         # The test server doesn't provide instructions, so it should be None
-        assert mcp_server.instructions is None
+        assert mcp_server.instructions == 'Be a helpful assistant.'
 
 
 async def test_agent_run_stream_with_mcp_server_http(allow_model_requests: None, model: Model):