Feat: A travel assistant demo implemented based on Google's official a2a-python SDK.

samples/a2a-python/README.md

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+# agent example
+
+The "example" under this directory is an agent-demo implemented based on the A2A standard protocol using the official Google SDK [a2a-python](https://github.com/google/a2a-python).
+
+
+## Prerequisites
+
+- Python 3.13 or higher
+- [UV](https://docs.astral.sh/uv/)
+- [a2a-python](https://github.com/google/a2a-python)
+
+
+## agent directory
+- [travel_planner](travel_planner/README.md)
+
+
+## License
+
+This project is licensed under the terms of the [Apache 2.0 License](/LICENSE).
+
+## Contributing
+
+See [CONTRIBUTING.md](/CONTRIBUTING.md) for contribution guidelines.

samples/a2a-python/travel_planner/README.md

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+# travel planner example
+> This is a Python implementation that adheres to the A2A (Assume to Answer) protocol. 
+> It is a travel assistant in line with the specifications of the OpenAI model, capable of providing you with travel planning services.
+> A travel assistant demo implemented based on Google's official a2a-python SDK.
+
+## Getting started
+
+1. update [config.json](config.json) with your own OpenAI API key etc.
+```json
+
+{
+  "model_name":"qwen3-32b",
+  "api_key": "sk-xxxx",
+  "base_url": "https://dashscope.aliyuncs.com/compatible-mode/v1"
+}
+
+```
+
+2. Start the server
+    ```bash
+    uv run .
+    ```
+
+3. Run the loop client
+    ```bash
+    uv run loop_client.py
+    ```
+
+
+## License
+
+This project is licensed under the terms of the [Apache 2.0 License](/LICENSE).
+
+## Contributing
+
+See [CONTRIBUTING.md](/CONTRIBUTING.md) for contribution guidelines.
+

samples/a2a-python/travel_planner/__main__.py

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+from agent_executor import TravelPlannerAgentExecutor
+
+from a2a.server.apps import A2AStarletteApplication
+from a2a.server.request_handlers import DefaultRequestHandler
+from a2a.server.tasks import InMemoryTaskStore
+from a2a.types import (
+    AgentAuthentication,
+    AgentCapabilities,
+    AgentCard,
+    AgentSkill,
+)
+
+
+if __name__ == '__main__':
+
+    skill = AgentSkill(
+        id='travel_planner',
+        name='travel planner agent',
+        description='travel planner',
+        tags=['travel planner'],
+        examples=['hello', 'nice to meet you!'],
+    )
+
+    agent_card = AgentCard(
+        name='travel planner Agent',
+        description='travel planner',
+        url='http://localhost:10001/',
+        version='1.0.0',
+        defaultInputModes=['text'],
+        defaultOutputModes=['text'],
+        capabilities=AgentCapabilities(streaming=True),
+        skills=[skill],
+        authentication=AgentAuthentication(schemes=['public']),
+    )
+
+
+    request_handler = DefaultRequestHandler(
+        agent_executor=TravelPlannerAgentExecutor(),
+        task_store=InMemoryTaskStore(),
+    )
+
+    server = A2AStarletteApplication(
+        agent_card=agent_card, http_handler=request_handler
+    )
+    import uvicorn
+
+    uvicorn.run(server.build(), host='0.0.0.0', port=10001)

samples/a2a-python/travel_planner/agent.py

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+from langchain_openai import ChatOpenAI
+from langchain_core.messages import HumanMessage, SystemMessage
+import json,asyncio
+from collections.abc import AsyncGenerator
+
+class TravelPlannerAgent:
+    """ travel planner Agent."""
+
+    def __init__(self):
+        """Initialize the travel dialogue model"""
+        try:
+            with open("config.json") as f:
+                config = json.load(f)
+            self.model = ChatOpenAI(
+                model=config["model_name"],
+                base_url=config["base_url"],
+                api_key=config["api_key"],
+                temperature=0.7  # Control the generation randomness (0-2, higher values indicate greater randomness)
+            )
+        except FileNotFoundError:
+            print("Error: The configuration file config.json cannot be found.")
+            exit()
+        except KeyError as e:
+            print(f"The configuration file is missing required fields: {e}")
+            exit()
+
+    async def stream(self, query: str) -> AsyncGenerator[str, None]:
+
+        """Stream the response of the large model back to the client. """
+        try:
+            # Initialize the conversation history (system messages can be added)
+            messages = [
+                SystemMessage(
+                    content="""
+                You are an expert travel assistant specializing in trip planning, destination information, 
+                and travel recommendations. Your goal is to help users plan enjoyable, safe, and 
+                realistic trips based on their preferences and constraints.
+
+                When providing information:
+                - Be specific and practical with your advice
+                - Consider seasonality, budget constraints, and travel logistics
+                - Highlight cultural experiences and authentic local activities
+                - Include practical travel tips relevant to the destination
+                - Format information clearly with headings and bullet points when appropriate
+
+                For itineraries:
+                - Create realistic day-by-day plans that account for travel time between attractions
+                - Balance popular tourist sites with off-the-beaten-path experiences
+                - Include approximate timing and practical logistics
+                - Suggest meal options highlighting local cuisine
+                - Consider weather, local events, and opening hours in your planning
+
+                Always maintain a helpful, enthusiastic but realistic tone and acknowledge 
+                any limitations in your knowledge when appropriate.
+                """
+                )
+            ]
+
+            # Add the user message to the history.
+            messages.append(HumanMessage(content=query))
+
+            # Invoke the model in streaming mode to generate a response.
+            for chunk in self.model.stream(messages):
+                # Return the text content block.
+                if hasattr(chunk, 'content') and chunk.content:
+                    yield {'content': chunk.content, 'done': False}
+            yield {'content': '', 'done': True}
+
+        except Exception as e:
+            print(f"error：{str(e)}")
+            yield {'content': 'Sorry, an error occurred while processing your request.', 'done': True}
+
+

samples/a2a-python/travel_planner/agent_executor.py

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+from uuid import uuid4
+from agent import TravelPlannerAgent
+
+from typing_extensions import override
+
+from a2a.types import (
+    TaskArtifactUpdateEvent,
+    TaskStatusUpdateEvent,
+)
+from a2a.server.agent_execution import AgentExecutor, RequestContext
+from a2a.server.events import EventQueue
+from a2a.utils import new_text_artifact
+
+
+class TravelPlannerAgentExecutor(AgentExecutor):
+    """travel planner AgentExecutor Example."""
+
+    def __init__(self):
+        self.agent = TravelPlannerAgent()
+
+    @override
+    async def execute(
+        self,
+        context: RequestContext,
+        event_queue: EventQueue,
+    ) -> None:
+        query = context.get_user_input()
+        if not context.message:
+            raise Exception('No message provided')
+
+        print(f'query:{query}')
+        print('answer:')
+        async for event in self.agent.stream(query):
+            print(event['content'])
+            message = TaskArtifactUpdateEvent(
+                contextId=context.context_id,
+                taskId=context.task_id,
+                artifact=new_text_artifact(
+                    name='current_result',
+                    text=event['content'],
+                ),
+            )
+            event_queue.enqueue_event(message)
+
+    @override
+    async def cancel(
+        self, context: RequestContext, event_queue: EventQueue
+    ) -> None:
+        raise Exception('cancel not supported')

samples/a2a-python/travel_planner/config.json

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+{
+  "model_name":"qwen3-32b",
+  "api_key": "sk-xxxx",
+  "base_url": "https://dashscope.aliyuncs.com/compatible-mode/v1"
+}

samples/a2a-python/travel_planner/loop_client.py

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+from a2a.client import A2AClient
+from typing import Any
+import httpx
+from uuid import uuid4
+import asyncio
+from a2a.types import (
+    MessageSendParams,
+    SendStreamingMessageRequest,
+)
+
+def print_welcome_message() -> None:
+    print("Welcome to the generic A2A client!")
+    print("Please enter your query (type 'exit' to quit):")
+
+def get_user_query() -> str:
+    return input("\n> ")
+
+async def interact_with_server(client: A2AClient) -> None:
+    while True:
+        user_input = get_user_query()
+        if user_input.lower() == 'exit':
+            print("bye!~")
+            break
+
+        send_message_payload: dict[str, Any] = {
+            'message': {
+                'role': 'user',
+                'parts': [
+                    {'type': 'text', 'text': user_input}
+                ],
+                'messageId': uuid4().hex,
+            },
+        }
+
+        try:
+            streaming_request = SendStreamingMessageRequest(
+                params=MessageSendParams(**send_message_payload)
+            )
+            stream_response = client.send_message_streaming(streaming_request)
+            async for chunk in stream_response:
+                print(get_response_text(chunk),  end='', flush=True)
+                await asyncio.sleep(0.1)
+        except Exception as e:
+            print(f"An error occurred: {e}")
+
+def get_response_text(chunk):
+    data = chunk.model_dump(mode='json', exclude_none=True)
+    return data['result']['artifact']['parts'][0]['text']
+
+
+async def main() -> None:
+    print_welcome_message()
+    async with httpx.AsyncClient() as httpx_client:
+        client = await A2AClient.get_client_from_agent_card_url(
+            httpx_client, 'http://localhost:10001'
+        )
+        await interact_with_server(client)
+
+
+if __name__ == '__main__':
+    asyncio.run(main())

samples/a2a-python/travel_planner/pyproject.toml

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+[project]
+name = "travel_planner"
+version = "0.1.0"
+description = "travel planner agent example that only returns Messages"
+readme = "README.md"
+requires-python = ">=3.13"
+dependencies = [
+    "a2a-sdk>=0.2.0",
+    "click>=8.1.8",
+    "dotenv>=0.9.9",
+    "httpx>=0.28.1",
+    "pydantic>=2.11.4",
+    "python-dotenv>=1.1.0",
+    "langchain-core>=0.2.31",
+    "langchain-openai>=0.1.26",
+    "langchain>=0.1.22",
+    "uvicorn>=0.34.2"
+]
+
+[tool.hatch.build.targets.wheel]
+packages = ["."]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"