先看类的定义头部：Agent 继承自 BaseAgent（agent/core.py:170），而 BaseAgent 是一个 Pydantic BaseModel（base_agent.py:200）：

# agent/core.py:170
class Agent(BaseAgent):
    """Represents an agent in a system.
    Each agent has a role, a goal, a backstory, and an optional language model (llm).
    The agent can also have memory, can operate in verbose mode, and can delegate tasks to other agents.
    """
    model_config = ConfigDict()

# base_agent.py:200
class BaseAgent(BaseModel, ABC, metaclass=AgentMeta):
    ...

最核心的四个字段在父类 BaseAgent（base_agent.py:262）：

# base_agent.py:262
id: UUID4 = Field(default_factory=uuid.uuid4, frozen=True)
role: str = Field(description="Role of the agent")
goal: str = Field(description="Objective of the agent")
backstory: str = Field(description="Backstory of the agent")
config: dict[str, Any] | None = Field(
    description="Configuration for the agent", default=None, exclude=True
)

这一组决定 Agent 干活时受哪些约束，全在 BaseAgent（base_agent.py:269）：

# base_agent.py:269
cache: bool = Field(
    default=True, description="Whether the agent should use a cache for tool usage.")
verbose: bool = Field(
    default=False, description="Verbose mode for the Agent Execution")
max_rpm: int | None = Field(
    default=None,
    description="Maximum number of requests per minute ... to be respected.")
allow_delegation: bool = Field(
    default=False,
    description="Enable agent to delegate and ask questions among each other.")
tools: list[BaseTool] | None = Field(
    default_factory=list, description="Tools at agents' disposal")
max_iter: int = Field(
    default=25, description="Maximum iterations for an agent to execute a task")

这一组在子类 Agent（agent/core.py:210）：

# agent/core.py:210
use_system_prompt: bool | None = Field(
    default=True, description="Use system prompt for the agent.")
llm: Annotated[
    str | BaseLLM | None,
    BeforeValidator(_validate_llm_ref),
    PlainSerializer(_serialize_llm_ref, return_type=dict | None, when_used="json"),
] = Field(description="Language model that will run the agent.", default=None)
function_calling_llm: Annotated[
    str | BaseLLM | None, ...
] = Field(
    ...,
    deprecated="function_calling_llm is deprecated and will be removed in a future release.")
# :228 三个模板字段
system_template: str | None = Field(default=None, description="System format for the agent.")
prompt_template: str | None = Field(default=None, description="Prompt format for the agent.")
response_template: str | None = Field(default=None, description="Response format for the agent.")

这一组是标准 Agent 的进阶能力（agent/core.py:242）：

# agent/core.py:242
respect_context_window: bool = Field(
    default=True,
    description="Keep messages under the context window size by summarizing content.")
max_retry_limit: int = Field(
    default=2, description="Maximum number of retries ... when an error occurs.")
inject_date: bool = Field(
    default=False, description="Whether to automatically inject the current date into tasks.")
# :268 计划相关
planning: bool = Field(
    default=False,
    description="Whether the agent should reflect and create a plan before executing a task.")
# :306 输出护栏
guardrail: Annotated[GuardrailType | None, ...] = Field(
    default=None,
    description="Function or string description of a guardrail to validate agent output")
guardrail_max_retries: int = Field(
    default=3, description="Maximum number of retries when guardrail fails")

Agent 是配置，那"干活的"是谁？看这两个字段（agent/core.py:333）：

# agent/core.py:333
agent_executor: CrewAgentExecutor | AgentExecutor | None = Field(
    default=None, description="An instance of the CrewAgentExecutor class.")
executor_class: Annotated[
    type[CrewAgentExecutor] | type[AgentExecutor],
    BeforeValidator(_validate_executor_class),
    PlainSerializer(_serialize_executor_class, return_type=str, when_used="json"),
] = Field(
    default=AgentExecutor,
    description="Class to use for the agent executor. Defaults to AgentExecutor ...")

而工具缓存/结果的容器在父类（base_agent.py:317）：

# base_agent.py:317
cache_handler: CacheHandler | None = Field(default=None, ...)
tools_handler: ToolsHandler = Field(default_factory=ToolsHandler, ...)
tools_results: list[dict[str, Any]] = Field(default_factory=list, ...)
# core.py:199 私有属性（下划线开头，不对外、不序列化）
_times_executed: int = PrivateAttr(default=0)
_last_messages: list[LLMMessage] = PrivateAttr(default_factory=list)