Pay-As-You-Go APIs for Autonomous AI Agents

1. Base URL & Header Credentials

All proxy endpoints use the standard marketplace host base. You must attach your custom developer key as an HTTP header name: X-Agent-API-Key.

2. Error Handlers

If an API request fails, the proxy forwards the original error status code where possible. However, if the agent runs out of wallet balance, the proxy returns a specific 402 Payment Required code.

3. LangChain Example Integration

Implement a custom python function inside LangChain tools or custom tools to make the call:

from langchain.agents import tool
import requests

@tool
def call_marketplace_api(api_name: str, query_params: dict = None) -> str:
    """Call a marketplace public API and pay per use. api_name should match explore catalog."""
    url = f"http://127.0.0.1:8000/api/proxy/{api_name}"
    headers = {
        "X-Agent-API-Key": "YOUR_DEVELOPER_API_KEY"
    }
    
    try:
        response = requests.get(url, headers=headers, params=query_params)
        if response.status_code == 402:
            return "Payment Required: Please notify user to top up their Easypaisa wallet."
        return response.text
    except Exception as e:
        return f"Error connecting to proxy: {str(e)}"