ResponsesAgent for Model Serving

MLflow 中的 ResponsesAgent 类提供了一个专门的接口，用于服务具有工具调用能力的、处理结构化响应的生成式 AI 模型。此代理旨在与 MLflow 的服务基础设施无缝协作，同时与 OpenAI 风格的 API 保持兼容。

概述

ResponsesAgent 扩展了 MLflow 的 PyFunc 模型接口，以支持需要高级功能（如多轮对话、工具调用、多代理编排以及与 OpenAI 的 Responses API 和 MLflow 模型跟踪的兼容性）的会话式 AI 应用程序。

• 📦 结构化请求/响应处理
• 🛠️ 工具调用和函数执行
• 💬 聊天历史管理
• 📊 Token 使用量跟踪
• 🤖 OpenAI API 兼容性
• 🔁 支持返回多个输出消息，包括来自工具调用的中间输出
• 👥 支持多代理场景
• 📚 与 MLflow 日志记录、跟踪和模型服务兼容
• 🔗 确保与 OpenAI Responses API 兼容，以便与下游客户端和 UI 无缝集成

这使其成为构建和部署聊天机器人、虚拟助手和其他会话式 AI 应用程序的理想选择。

主要特性

结构化响应处理

ResponsesAgent 处理符合聊天补全标准的结构化输入和输出

• 消息：处理具有基于角色的消息（系统、用户、助手）的对话历史记录
• 工具调用：支持带有结构化参数的函数调用
• 使用量跟踪：监控 Token 消耗和模型性能
• 元数据：捕获额外的上下文和配置

OpenAI API 兼容性

ResponsesAgent 的设计充分考虑了 OpenAI API 的兼容性，允许与为 OpenAI 的聊天补全 API 构建的现有应用程序和工具无缝集成。这种兼容性涵盖请求格式、响应结构和 API 端点。

MLflow 集成

与 MLflow 生态系统完全集成，包括

• 📈 模型跟踪和版本控制
• 🧪 实验管理
• 🗃️ 模型注册表
• 🚀 部署选项

基本用法

实现 ResponsesAgent

入门

要创建您自己的代理，请继承 mlflow.pyfunc.ResponsesAgent 并实现 predict 方法中的代理逻辑。实现是框架无关的，允许您使用任何代理编写框架。请注意，使用 ResponsesAgent 需要 pydantic>=2。有关调用 Chat Completions LLM、Responses API LLM、包装 LangGraph 代理和工具调用代理的示例实现，请参阅下面的 代码片段。

创建代理输出

在实现代理时，您将使用两种主要的输出类型：ResponsesAgentResponse 和 ResponsesAgentStreamEvent。这些是您应该直接创建的唯一 pydantic 对象。mlflow.types.responses_helpers 中的其余类仅用于验证字典。

如果您想返回不符合标准接口的输出，可以使用 custom_outputs 字段。

以下是一些您可以在 ResponsesAgent 接口中用于创建常见输出的辅助方法

• mlflow.pyfunc.ResponsesAgent.create_reasoning_item()
• mlflow.pyfunc.ResponsesAgent.create_text_output_item()
• mlflow.pyfunc.ResponsesAgent.create_function_call_item()
• mlflow.pyfunc.ResponsesAgent.create_function_call_output_item()
• mlflow.pyfunc.ResponsesAgent.create_text_delta()（仅用于流式传输）
• mlflow.pyfunc.ResponsesAgent.create_annotation_added()（仅用于流式传输）

这是一个使用 ResponsesAgentResponse 和自定义输出的完整工具调用序列示例

from mlflow.pyfunc import ResponsesAgent
from mlflow.types.responses import ResponsesAgentRequest, ResponsesAgentResponse


class SimpleResponsesAgent(ResponsesAgent):
    @mlflow.trace(span_type=SpanType.AGENT)
    def predict(self, request: ResponsesAgentRequest) -> ResponsesAgentResponse:
        return ResponsesAgentResponse(
            output=[
                self.create_function_call_item(
                    id="fc_1",
                    call_id="call_1",
                    name="python_exec",
                    arguments='{"code":"result = 4 * 3\\nprint(result)"}',
                ),
                self.create_function_call_output_item(
                    call_id="call_1",
                    output="12\n",
                ),
                self.create_text_output_item(
                    text="The result of 4 * 3 in Python is 12.",
                    id="msg_1",
                ),
            ],
            custom_outputs={"key1": "custom-value1"},
        )

流式传输代理输出

对于实时处理，您可以使用流式传输事件而不是返回完整响应。流式传输允许您在部分结果可用时发送它们，这对于长时间运行的操作或您想向用户显示进度的场景很有用。

基本文本流式传输

要在 ResponsesAgent 接口中流式传输文本，您应该

• yield response.output_text.delta 事件，其中包含可用时的数据块
  • 必须有一个 item_id，将相关事件与单个输出项关联起来
• yield response.output_item.done 事件以汇总所有数据块

from mlflow.types.responses import ResponsesAgentStreamEvent


class SimpleResponsesAgent(ResponsesAgent):
    # ... continuing from above
    @mlflow.trace(span_type=SpanType.AGENT)
    def predict_stream(
        self, request: ResponsesAgentRequest
    ) -> Generator[ResponsesAgentStreamEvent, None, None]:
        # stream text, all with the same item_id
        yield ResponsesAgentStreamEvent(
            **self.create_text_delta(delta="Hello", item_id="msg_1"),
        )
        yield ResponsesAgentStreamEvent(
            **self.create_text_delta(delta="world", item_id="msg_1"),
        )
        yield ResponsesAgentStreamEvent(
            **self.create_text_delta(delta="!", item_id="msg_1"),
        )

        # the text output item id should be the same
        # item_id as the streamed text deltas
        yield ResponsesAgentStreamEvent(
            type="response.output_item.done",
            item=self.create_text_output_item(
                text="Hello world!",
                id="msg_1",
            ),
        )

带有流式传输的工具调用

您还可以流式传输工具调用及其结果。每个工具调用及其输出都作为单独的 response.output_item.done 事件发送。这使得 MLflow 跟踪成为可能，并使客户端更容易重建流式消息历史记录。

from mlflow.types.responses import ResponsesAgentStreamEvent


class SimpleResponsesAgent(ResponsesAgent):
    # ... continuing from above
    @mlflow.trace(span_type=SpanType.AGENT)
    def predict_stream(
        self, request: ResponsesAgentRequest
    ) -> Generator[ResponsesAgentStreamEvent, None, None]:
        yield ResponsesAgentStreamEvent(
            type="response.output_item.done",
            item=self.create_function_call_item(
                id="fc_1",
                call_id="call_1",
                name="python_exec",
                arguments='{"code":"result = 4 * 3\\nprint(result)"}',
            ),
        )
        yield ResponsesAgentStreamEvent(
            type="response.output_item.done",
            item=self.create_function_call_output_item(
                call_id="call_1",
                output="12\n",
            ),
        )
        yield ResponsesAgentStreamEvent(
            type="response.output_item.done",
            item=self.create_text_output_item(
                text="The result of 4 * 3 in Python is 12.",
                id="msg_1",
            ),
        )

日志记录和模型服务

使用 代码模型 方法记录您的代理。此方法是框架无关的，并支持所有编写框架

with mlflow.start_run():
    logged_agent_info = mlflow.pyfunc.log_model(
        python_model="agent.py",  # replace with your relative path to agent code
        name="agent",
    )

为了方便使用，MLflow 内置了以下功能

• 自动模型签名推断
  • 将符合 ResponsesAgentRequest 和 ResponsesAgentResponse 架构的输入和输出签名设置好
• 元数据
  • {"task": "agent/v1/responses"} 将自动附加到您在记录模型时可能传入的任何元数据
• 输入示例
  • 提供输入示例是可选的，将默认使用 mlflow.types.responses.RESPONSES_AGENT_INPUT_EXAMPLE
  • 如果您确实提供了输入示例，请确保它是符合 ResponsesAgentRequest 架构的字典

要测试 ResponsesAgent，您可以在记录它之前和之后传递一个遵循 ResponsesAgentRequest 架构的单个输入字典

import mlflow

# load it back from mlflow
loaded_model = mlflow.pyfunc.load_model(logged_agent_info.model_uri)
loaded_model.predict(
    {
        "input": [{"role": "user", "content": "what is 4*3 in python"}],
        "context": {"conversation_id": "123", "user_id": "456"},
    }
)

要服务模型，请参阅 服务选项 以获取详细说明。

示例

使用 ChatCompletions LLM 的简单聊天示例

这是一个调用 OpenAI 的 gpt-5 模型并使用 ChatCompletions API 的代理示例

import mlflow
from mlflow.models import set_model
from mlflow.pyfunc import ResponsesAgent
from mlflow.types.responses import (
    ResponsesAgentRequest,
    ResponsesAgentResponse,
    output_to_responses_items_stream,
    to_chat_completions_input,
)
from openai import OpenAI

client = OpenAI()


class SimpleResponsesAgent(ResponsesAgent):
    def call_llm(self, messages):
        for chunk in client.chat.completions.create(
            model="gpt-5",
            messages=messages,
            stream=True,
        ):
            yield chunk.to_dict()

    def predict(self, request: ResponsesAgentRequest):
        outputs = [
            event.item
            for event in self.predict_stream(request)
            if event.type == "response.output_item.done"
        ]
        return ResponsesAgentResponse(
            output=outputs, custom_outputs=request.custom_inputs
        )

    def predict_stream(self, request: ResponsesAgentRequest):
        messages = to_chat_completions_input([i.model_dump() for i in request.input])

        yield from output_to_responses_items_stream(self.call_llm(messages))


mlflow.openai.autolog()
agent = SimpleResponsesAgent()
set_model(agent)

使用 Responses API LLM 的简单聊天示例

这是一个调用 OpenAI 的 gpt-4o 模型并使用 Responses API 的代理示例

# uncomment below if running inside a jupyter notebook
# %%writefile agent.py
import os
from typing import Generator

import mlflow
from mlflow.entities.span import SpanType
from mlflow.models import set_model
from mlflow.pyfunc.model import ResponsesAgent
from mlflow.types.responses import (
    ResponsesAgentRequest,
    ResponsesAgentResponse,
    ResponsesAgentStreamEvent,
)
from openai import OpenAI


class SimpleResponsesAgent(ResponsesAgent):
    def __init__(self, model: str):
        self.client = OpenAI()
        self.model = model

    @mlflow.trace(span_type=SpanType.AGENT)
    def predict(self, request: ResponsesAgentRequest) -> ResponsesAgentResponse:
        response = self.client.responses.create(input=request.input, model=self.model)
        return ResponsesAgentResponse(**response.to_dict())

    @mlflow.trace(span_type=SpanType.AGENT)
    def predict_stream(
        self, request: ResponsesAgentRequest
    ) -> Generator[ResponsesAgentStreamEvent, None, None]:
        for event in self.client.responses.create(
            input=request.input, stream=True, model=self.model
        ):
            yield ResponsesAgentStreamEvent(**event.to_dict())


mlflow.openai.autolog()
agent = SimpleResponsesAgent(model="gpt-4o")
set_model(agent)

包装 LangGraph 代理

这是一个在 ResponsesAgent 中包装 LangGraph 代理的示例

from typing import Generator

import mlflow
from langgraph.graph.state import CompiledStateGraph
from mlflow.models import set_model
from mlflow.pyfunc import ResponsesAgent
from mlflow.types.responses import (
    ResponsesAgentRequest,
    ResponsesAgentResponse,
    ResponsesAgentStreamEvent,
    output_to_responses_items_stream,
    to_chat_completions_input,
)


class LangGraphResponsesAgent(ResponsesAgent):
    def __init__(self, agent: CompiledStateGraph):
        self.agent = agent

    def predict(self, request: ResponsesAgentRequest) -> ResponsesAgentResponse:
        outputs = [
            event.item
            for event in self.predict_stream(request)
            if event.type == "response.output_item.done"
        ]
        return ResponsesAgentResponse(
            output=outputs, custom_outputs=request.custom_inputs
        )

    def predict_stream(
        self,
        request: ResponsesAgentRequest,
    ) -> Generator[ResponsesAgentStreamEvent, None, None]:
        cc_msgs = to_chat_completions_input([i.model_dump() for i in request.input])

        for _, events in self.agent.stream(
            {"messages": cc_msgs}, stream_mode=["updates"]
        ):
            for node_data in events.values():
                yield from output_to_responses_items_stream(node_data["messages"])


mlflow.langchain.autolog()
graph = None  # TODO: replace with your compiled LangGraph agent
agent = LangGraphResponsesAgent(graph)
set_model(agent)

工具调用示例

这是一个调用 OpenAI 的 gpt-4o 模型并使用简单工具的代理示例

# uncomment below if running inside a jupyter notebook
# %%writefile agent.py
import json
from typing import Any, Callable, Generator
import os
from uuid import uuid4

import backoff
import mlflow
import openai
from mlflow.entities import SpanType
from mlflow.pyfunc import ResponsesAgent
from mlflow.types.responses import (
    ResponsesAgentRequest,
    ResponsesAgentResponse,
    ResponsesAgentStreamEvent,
)
from openai import OpenAI
from pydantic import BaseModel


class ToolInfo(BaseModel):
    """
    Class representing a tool for the agent.
    - "name" (str): The name of the tool.
    - "spec" (dict): JSON description of the tool (matches OpenAI Responses format)
    - "exec_fn" (Callable): Function that implements the tool logic
    """

    name: str
    spec: dict
    exec_fn: Callable


class ToolCallingAgent(ResponsesAgent):
    """
    Class representing a tool-calling Agent
    """

    def __init__(self, model: str, tools: list[ToolInfo]):
        """Initializes the ToolCallingAgent with tools."""
        self.model = model
        self.client: OpenAI = OpenAI()
        self._tools_dict = {tool.name: tool for tool in tools}

    def get_tool_specs(self) -> list[dict]:
        """Returns tool specifications in the format OpenAI expects."""
        return [tool_info.spec for tool_info in self._tools_dict.values()]

    @mlflow.trace(span_type=SpanType.TOOL)
    def execute_tool(self, tool_name: str, args: dict) -> Any:
        """Executes the specified tool with the given arguments."""
        return self._tools_dict[tool_name].exec_fn(**args)

    @backoff.on_exception(backoff.expo, openai.RateLimitError)
    @mlflow.trace(span_type=SpanType.LLM)
    def call_llm(self, input_messages) -> ResponsesAgentStreamEvent:
        return (
            self.client.responses.create(
                model=self.model,
                input=input_messages,
                tools=self.get_tool_specs(),
            )
            .output[0]
            .model_dump(exclude_none=True)
        )

    def handle_tool_call(self, tool_call: dict[str, Any]) -> ResponsesAgentStreamEvent:
        """
        Execute tool calls and return a ResponsesAgentStreamEvent w/ tool output
        """
        args = json.loads(tool_call["arguments"])
        result = str(self.execute_tool(tool_name=tool_call["name"], args=args))

        tool_call_output = {
            "type": "function_call_output",
            "call_id": tool_call["call_id"],
            "output": result,
        }
        return ResponsesAgentStreamEvent(
            type="response.output_item.done", item=tool_call_output
        )

    def call_and_run_tools(
        self,
        input_messages,
        max_iter: int = 10,
    ) -> Generator[ResponsesAgentStreamEvent, None, None]:
        for _ in range(max_iter):
            last_msg = input_messages[-1]
            if (
                last_msg.get("type", None) == "message"
                and last_msg.get("role", None) == "assistant"
            ):
                return
            if last_msg.get("type", None) == "function_call":
                tool_call_res = self.handle_tool_call(last_msg)
                input_messages.append(tool_call_res.item)
                yield tool_call_res
            else:
                llm_output = self.call_llm(input_messages=input_messages)
                input_messages.append(llm_output)
                yield ResponsesAgentStreamEvent(
                    type="response.output_item.done",
                    item=llm_output,
                )

        yield ResponsesAgentStreamEvent(
            type="response.output_item.done",
            item={
                "id": str(uuid4()),
                "content": [
                    {
                        "type": "output_text",
                        "text": "Max iterations reached. Stopping.",
                    }
                ],
                "role": "assistant",
                "type": "message",
            },
        )

    @mlflow.trace(span_type=SpanType.AGENT)
    def predict(self, request: ResponsesAgentRequest) -> ResponsesAgentResponse:
        outputs = [
            event.item
            for event in self.predict_stream(request)
            if event.type == "response.output_item.done"
        ]
        return ResponsesAgentResponse(
            output=outputs, custom_outputs=request.custom_inputs
        )

    @mlflow.trace(span_type=SpanType.AGENT)
    def predict_stream(
        self, request: ResponsesAgentRequest
    ) -> Generator[ResponsesAgentStreamEvent, None, None]:
        input_messages = [{"role": "system", "content": SYSTEM_PROMPT}] + [
            i.model_dump() for i in request.input
        ]
        yield from self.call_and_run_tools(input_messages=input_messages)


tools = [
    ToolInfo(
        name="get_weather",
        spec={
            "type": "function",
            "name": "get_weather",
            "description": "Get current temperature for provided coordinates in celsius.",
            "parameters": {
                "type": "object",
                "properties": {
                    "latitude": {"type": "number"},
                    "longitude": {"type": "number"},
                },
                "required": ["latitude", "longitude"],
                "additionalProperties": False,
            },
            "strict": True,
        },
        exec_fn=lambda latitude, longitude: 70,  # dummy tool implementation
    )
]

os.environ["OPENAI_API_KEY"] = "your OpenAI API key"

SYSTEM_PROMPT = "You are a helpful assistant that can call tools to get information."
mlflow.openai.autolog()
AGENT = ToolCallingAgent(model="gpt-4o", tools=tools)
mlflow.models.set_model(AGENT)

服务选项

本地服务

为开发和测试启动本地服务器

mlflow models serve -m models:/<model_id> -p 5000

测试已服务的模型

import requests

response = requests.post(
    "https://:5000/invocations",
    json={"messages": [{"role": "user", "content": "What's the weather like?"}]},
)

print(response.json())

Docker 部署

mlflow models build-docker -m runs:/<run_id>/responses_agent -n my-responses-agent
docker run -p 5000:8080 my-responses-agent

Databricks 模型服务

注意

Databricks 的托管 MLflow 服务提供端点创建和管理功能，但在开源 MLflow 中不提供。

前提条件：将已记录的模型注册到 Databricks-UC

import mlflow

mlflow.register_model("model:/<model_id>", "<catalog>.<schema>.<model_name>")

对于 Databricks 上的托管 MLflow，ResponsesAgent 模型与 Databricks 模型服务无缝集成

from mlflow.deployments import get_deploy_client

client = get_deploy_client("databricks")
endpoint = client.create_endpoint(
    name="unity-catalog-model-endpoint",
    config={
        "served_entities": [
            {
                "name": "ads-entity",
                "entity_name": "catalog.schema.my-ads-model",
                "entity_version": "3",
                "workload_size": "Small",
                "scale_to_zero_enabled": True,
            }
        ],
        "traffic_config": {
            "routes": [
                {"served_model_name": "my-ads-model-3", "traffic_percentage": 100}
            ]
        },
    },
)

架构和类型

ResponsesAgent 使用结构化架构进行请求和响应，有关详细结构，请参阅 ResponsesAgentRequest 和 ResponsesAgentResponse。

# Example Request schema
{
    "input": [
        {
            "role": "user",
            "content": "What is the weather like in Boston today?",
        }
    ],
    "tools": [
        {
            "type": "function",
            "name": "get_current_weather",
            "parameters": {
                "type": "object",
                "properties": {"location": {"type": "string"}},
                "required": ["location", "unit"],
            },
        }
    ],
}

# Example Response schema
{
    "output": [
        {
            "type": "message",
            "id": "some-id",
            "status": "completed",
            "role": "assistant",
            "content": [
                {
                    "type": "output_text",
                    "text": "rainy",
                }
            ],
        }
    ],
}

故障排除

常见问题

1. 导入错误：确保所有依赖项都包含在 conda 环境中
2. 架构验证：验证输入/输出格式是否与预期架构匹配
3. 模型记录问题：使用 代码模型 功能来记录模型
4. 缺少跟踪：通过 mlflow.<flavor>.autolog 或手动跟踪 mlflow.start_span 来启用跟踪

调试

启用 跟踪 进行故障排除，如果您的模型被跟踪

import mlflow

# enable autologging if your agent internally uses MLflow tracing-supported libraries internally, such as LangChain, OpenAI, etc.
# mlflow.<flavor>.autolog()

# Test your agent locally before serving
agent = MyResponsesAgent()
agent.predict(
    {
        "input": [{"role": "user", "content": "what is 4*3 in python"}],
        "context": {"conversation_id": "123", "user_id": "456"},
    }
)