Half an MCP configuration

A developer connected a remote MCP server so the agent could file tickets. The request is rejected as invalid, and the error mentions the toolset.

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=16000,
    betas=["mcp-client-2025-11-20"],
    mcp_servers=[
        {"type": "url", "name": "tracker", "url": "https://mcp.example.com/sse"}
    ],
    messages=messages,
)