from dotenv import load_dotenv

load_dotenv()

True

import os, asyncio, json

from langchain.chat_models import init_chat_model
from langchain.agents import create_agent
from langchain.messages import HumanMessage, AIMessage
from langchain.tools import tool
from langchain_mcp_adapters.client import MultiServerMCPClient
from langgraph.checkpoint.memory import InMemorySaver

from typing import Dict, Any
from tavily import TavilyClient
from pprint import pprint



DEEPSEEK_MODEL = "deepseek-chat"
DEEPSEEK_BASE_URL = "https://api.deepseek.com"

def deepseek_model(model: str = DEEPSEEK_MODEL, max_tokens=1000, **kwargs):
    return init_chat_model(
        model=model,
        # DeepSeek uses LangChain's OpenAI-compatible transport.
        model_provider="openai",
        api_key=os.environ["DEEPSEEK_API_KEY"],
        base_url=DEEPSEEK_BASE_URL,
        max_tokens=max_tokens,
        **kwargs,
    )

client = MultiServerMCPClient(
    {
        "travel_server": {
                "transport": "sse",
                "url": "https://mcp.kiwi.com"
            }
    }
)

tools = await client.get_tools()

for msg in tools:
    pprint(msg.name)
    print()

'search-flight'

'feedback-to-devs'

agent = create_agent(
    deepseek_model(),
    tools=tools, # main purpose to use a MCP
    checkpointer=InMemorySaver(),
    system_prompt="You are a travel agent. No follow up questions."
)

config = {"configurable": {"thread_id": "1"}}

response = await agent.ainvoke(
    {"messages": [HumanMessage(content="Get me a return flight from Melbourne to Changsha on Sep 1st 2026 and return on Sep 18st 2026.")]},
    config
    )

print(response["messages"][-1].content)

I've already searched for this route earlier! Here's a comprehensive overview of the return flight options from Melbourne to Changsha on Sep 1st, returning Sep 18th, 2026. Please note there are **no direct flights** — all have at least one layover.

---

## 🌏 Return Flights: Melbourne (MEL) → Changsha (CSX) → Melbourne (MEL)

### 💰 Best Prices

| Outbound | Return | Total | Book |
|---|---|---|---|
| **MEL 01/09 13:00 → SIN → CSX 02/09 23:05** (36h 05m) | **CSX 18/09 07:50 → PVG → MEL 19/09 09:00** (23h 10m) | **$706** | [Book](https://on.kiwi.com/CVWloJ) |
| **MEL 01/09 13:00 → SIN → CSX 02/09 23:05** (36h 05m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$708** | [Book](https://on.kiwi.com/h51AxI) |
| **MEL 01/09 21:35 → SIN → CSX 02/09 23:05** (27h 30m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$774** | [Book](https://on.kiwi.com/kmmMz9) |
| **MEL 01/09 20:20 → TFU → CSX 02/09 10:20** (16h 00m) | **CSX 18/09 18:10 → TFU → MEL 19/09 14:10** (18h 00m) | **$741** | [Book](https://on.kiwi.com/iMWWDI) |
| **MEL 01/09 11:00 → PVG → CSX 02/09 00:25** (15h 25m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$908** | [Book](https://on.kiwi.com/psHzZT) |
| **MEL 01/09 09:15 → SIN → CSX 01/09 23:05** (15h 50m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$963** | [Book](https://on.kiwi.com/zAmYKF) |

### ⚡ Shortest Travel Times

| Outbound | Return | Total | Book |
|---|---|---|---|
| **MEL 01/09 23:45 → HKG → CSX 02/09 11:05** (13h 20m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$1,048** | [Book](https://on.kiwi.com/vMZsQz) |
| **MEL 01/09 11:00 → PVG → CSX 02/09 00:25** (15h 25m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$908** | [Book](https://on.kiwi.com/psHzZT) |
| **MEL 01/09 09:15 → SIN → CSX 01/09 23:05** (15h 50m) | **CSX 18/09 14:10 → PVG → MEL 19/09 09:00** (16h 50m) | **$963** | [Book](https://on.kiwi.com/zAmYKF) |
| **MEL 01/09 20:20 → TFU → CSX 02/09 10:20** (16h 00m) | **CSX 18/09 18:10 → TFU → MEL 19/09 14:10** (18h 00m) | **$741** | [Book](https://on.kiwi.com/iMWWDI) |

### 🏆 My Top Picks

| Recommendation | Route | Price | Why |
|---|---|---|---|
| **🥇 Best Overall Value** | **MEL → PVG → CSX** + **CSX → PVG → MEL** | **$908** | Great balance of price (15h outbound, 16h 50m return) — both via Shanghai |
| **🥇 Cheapest** | **MEL → SIN → CSX** + **CSX → PVG → MEL** | **$706** | Cheapest total, but long outbound layover |
| **🥇 Shortest Trip** | **MEL → HKG → CSX** + **CSX → PVG → MEL** | **$1,048** | Fastest outbound at only 13h 20m via Hong Kong |
| **🥇 Chengdu Route** | **MEL → TFU → CSX** + **CSX → TFU → MEL** | **$741** | Good price, both ways via Chengdu — consistent route |

> **Fun fact about Changsha:** Changsha is home to **Orange Island (Júzi Zhōu)** — a massive island in the Xiang River that features a giant young Mao Zedong statue! The island gets its name from the plentiful orange trees that grow there. 🍊

Have a fantastic trip to Changsha! Let me know if you'd like to book any of these options! ✈️🎉