langchain-ausca

LangChain tools that pay for HTTP 402 APIs over x402 instead of carrying API keys. A tool built here works against any x402 v2 resource; nothing in it is specific to one vendor. The model authors the request; the caller's signing key and hard per-call USD cap stay outside the model's reach, enforced by the official x402 library's spend controls before anything is signed.

Install

pip install langchain-ausca

Use

import os
from langchain_ausca import payable_tool
from pydantic import BaseModel

class LeaseBrowser(BaseModel):
    duration_seconds: int

browser = payable_tool(
    name="lease_browser",
    description="Lease a remote browser with CDP access for 10, 30, or 60 minutes. Costs $0.10 to $0.25 in USDC on Base.",
    args_schema=LeaseBrowser,
    url="https://ausca.com/v1/lease-browser",
    private_key=os.environ["WALLET_PRIVATE_KEY"],  # pays USDC on Base
    max_payment_usd=0.50,                          # hard per-call cap
)

The tool result is a JSON string with the resource result and, when the call was paid, the decoded settlement proof from the PAYMENT-RESPONSE header.

The example uses Ausca, pay-per-call agent infrastructure services with no accounts or API keys; its catalog-bound Python client is the ausca package. Any other x402 v2 resource works the same way: point url at it.

The npm sibling of this package is langchain-ausca.

License

MIT