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The MCPAgent supports structured output, allowing you to get strongly-typed Pydantic models instead of plain text responses. The agent becomes schema-aware and will intelligently retry to gather missing information until all required fields can be populated.

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How it Works

When you provide an output_schema parameter, the agent:
  1. Understands requirements - The agent knows exactly what information it needs to collect
  2. Attempts structured output - At completion points, tries to format the result into your schema
  3. Intelligently retries - If required fields are missing, continues execution to gather the missing data
  4. Validates completeness - Only finishes when all required fields can be populated

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Basic Example

import asyncio
from pydantic import BaseModel, Field
from langchain_openai import ChatOpenAI
from mcp_use import MCPAgent, MCPClient

class WeatherInfo(BaseModel):
    """Weather information for a location"""
    city: str = Field(description="City name")
    temperature: float = Field(description="Temperature in Celsius")
    condition: str = Field(description="Weather condition")
    humidity: int = Field(description="Humidity percentage")

async def main():
    # Setup client and agent
    client = MCPClient(config={"mcpServers": {...}})
    llm = ChatOpenAI(model="gpt-4o")
    agent = MCPAgent(llm=llm, client=client)

    # Get structured output
    weather: WeatherInfo = await agent.run(
        "Get the current weather in San Francisco",
        output_schema=WeatherInfo
    )

    print(f"Temperature in {weather.city}: {weather.temperature}°C")
    print(f"Condition: {weather.condition}")
    print(f"Humidity: {weather.humidity}%")

asyncio.run(main())

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Key Benefits

  • Type Safety: Get Pydantic (Python) or Zod (TypeScript) models with full IDE support and validation
  • Intelligent Gathering: Agent knows what information is required and won’t stop until it has everything
  • Automatic Retry: Missing fields trigger continued execution automatically
  • Field Validation: Built-in validation for required fields, data types, and constraints
The agent will continue working until all required fields in your schema can be populated, ensuring you always get complete, structured data.