Pydantic AI 的 Capabilities 机制是如何工作的？

from pydantic_ai import Agent
from pydantic_ai.capabilities import Capability, Thinking, ToolSearch, WebSearch

agent = Agent(
    'anthropic:claude-opus-4-7',
    instructions='Research thoroughly and cite your sources.',
    capabilities=[
        Thinking(effort='high'),
        WebSearch(),
        ToolSearch(),
        Capability(
            id='github',
            description='Look up GitHub issues, pull requests, and code.',
            instructions='Use the GitHub tools when a question is about a repository.',
            toolset=MCPToolset('https://mcp.example.com/github'),
            defer_loading=True,
        ),
    ],
)