建立訊息並呼叫 LLM
你已經建立好 get_context_from_mcp(user_query) 輔助函式,會回傳資源文字與提示文字,現在該把這些資訊傳給 LLM 了!
貨幣伺服器、get_context_from_mcp()、get_tools_from_mcp()、call_mcp_tool(),以及 Claude 用戶端都已在背景設定完成。你需要完成這個函式:負責組合提示、呼叫模型,並處理直接回覆或工具呼叫。題目提供了含糊與明確兩種使用者輸入,看看你的 MCP 提示是否產生效果!
本練習屬於課程
Model Context Protocol(MCP)入門
練習說明
- 在第 37 行,將
prompt_text、字串 "\n\nSupported currencies:\n",以及resource_text串接起來,建立full_prompt。 - 在第 47 行,將
full_prompt(作為使用者訊息內容)與anthropic_tools清單一併送到模型。 - 在第 52–55 行,若回應的
stop_reason為 "end_turn",回傳str(text)。 - 在第 58–60 行,若回應的
stop_reason為 "tool_use",將工具使用區塊的.name與.input傳給call_mcp_tool()。
動手互動練習
試著完成這個範例程式碼,體驗一下這個練習。
from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client
async def get_context_from_mcp(user_query: str) -> tuple[str, str]:
params = StdioServerParameters(command=sys.executable, args=["currency_server.py"])
async with stdio_client(params) as (reader, writer):
async with ClientSession(reader, writer) as session:
await session.initialize()
resource_result = await session.read_resource("file://currencies.txt")
resource_text = resource_result.contents[0].text
prompt_result = await session.get_prompt("convert_currency_prompt",
arguments={"currency_request": user_query})
prompt_text = prompt_result.messages[0].content.text
return resource_text, prompt_text
async def get_tools_from_mcp():
params = StdioServerParameters(command=sys.executable, args=["currency_server.py"])
async with stdio_client(params) as (reader, writer):
async with ClientSession(reader, writer) as session:
await session.initialize()
response = await session.list_tools()
return response.tools
async def call_mcp_tool(tool_name: str, arguments: dict) -> str:
params = StdioServerParameters(command=sys.executable, args=["currency_server.py"])
async with stdio_client(params) as (reader, writer):
async with ClientSession(reader, writer) as session:
await session.initialize()
result = await session.call_tool(tool_name, arguments)
return str(result.content[0].text)
async def call_llm_with_context(user_query: str):
"""Call the LLM with resource and prompt context from MCP."""
resource_text, prompt_text = await get_context_from_mcp(user_query)
# Combine the resource and prompt text
full_prompt = ____ + "\n\nSupported currencies:\n" + ____
client = AsyncAnthropic(api_key="")
mcp_tools = await get_tools_from_mcp()
anthropic_tools = [{"name": t.name, "description": t.description or "", "input_schema": t.inputSchema} for t in mcp_tools]
# Send full_prompt (as a user message) and the tools list to the model
response = await client.messages.create(
model="claude-sonnet-4-6",
max_tokens=1024,
messages=[{"role": "user", "content": ____}],
tools=anthropic_tools,
)
# Return the text response
if response.stop_reason == "____":
text = next((block.text for block in response.content if block.type == "text"), "")
print(f"\nAssistant: {text}")
return str(____)
# Call the tool requested in the LLM's tool use
if response.stop_reason == "____":
tool_use = next(block for block in response.content if block.type == "tool_use")
result = await call_mcp_tool(____.name, ____)
followup = await client.messages.create(
model="claude-sonnet-4-6",
max_tokens=1024,
messages=[
{"role": "user", "content": full_prompt},
{"role": "assistant", "content": response.content},
{"role": "user", "content": [{"type": "tool_result", "tool_use_id": tool_use.id, "content": result}]},
],
tools=anthropic_tools,
)
final_text = next((block.text for block in followup.content if block.type == "text"), None)
if final_text:
print(f"\nAssistant: {final_text}")
return str(final_text)
print("=== Ambiguous request (prompt asks for clarification) ===")
asyncio.run(call_llm_with_context("Convert some euros to dollars"))
print("\n=== Unambiguous request (model calls tool) ===")
asyncio.run(call_llm_with_context("How much is 50 GBP in euros?"))