web42-auth (Python)

Token introspection client and framework middleware helpers for the Web42 auth platform.

Installation

# Core client only
pip install web42-auth

# With FastAPI middleware
pip install 'web42-auth[fastapi]'

# With Flask middleware
pip install 'web42-auth[flask]'

# With A2A server support (includes uvicorn)
pip install 'web42-auth[a2a]'

# Everything
pip install 'web42-auth[all]'

Quick start

from web42_auth import Web42Client

client = Web42Client(
    client_id="your-client-id",
    client_secret="your-client-secret",
)

token_info = client.introspect("Bearer eyJ...")
if token_info.active:
    print(token_info.sub)  # subject (user/agent ID)

Async

from web42_auth import AsyncWeb42Client

client = AsyncWeb42Client(
    client_id="your-client-id",
    client_secret="your-client-secret",
)

token_info = await client.introspect("eyJ...")

Reference

Web42Client / AsyncWeb42Client

Methods:

• introspect(token: str) -> TokenInfo — validate a Bearer token

TokenInfo

Web42AuthError

Raised when the auth server returns an unexpected error response.

FastAPI middleware

import os
from fastapi import FastAPI
from web42_auth import AsyncWeb42Client
from web42_auth.middleware.fastapi import make_require_token

w42 = AsyncWeb42Client(
    client_id=os.environ["WEB42_CLIENT_ID"],
    client_secret=os.environ["WEB42_CLIENT_SECRET"],
)

app = FastAPI()
require_token = make_require_token(w42)

@app.get("/protected", dependencies=[Depends(require_token)])
async def protected():
    return {"status": "ok"}

Environment variables: WEB42_CLIENT_ID, WEB42_CLIENT_SECRET

Flask middleware

import os
from flask import Flask
from web42_auth import Web42Client
from web42_auth.middleware.flask import Web42FlaskMiddleware

w42 = Web42Client(
    client_id=os.environ["WEB42_CLIENT_ID"],
    client_secret=os.environ["WEB42_CLIENT_SECRET"],
)

app = Flask(__name__)
Web42FlaskMiddleware(app, client=w42)

A2A server

Build an A2A-protocol agent server with Web42 Bearer auth enforced on every request:

import os
from web42_auth import AsyncWeb42Client
from web42_auth.a2a import create_a2a_server, AgentCardOptions

w42 = AsyncWeb42Client(
    client_id=os.environ["WEB42_CLIENT_ID"],
    client_secret=os.environ["WEB42_CLIENT_SECRET"],
)

server = create_a2a_server(
    web42=w42,
    card=AgentCardOptions(
        name="My Agent",
        description="Does cool things",
        base_url="http://localhost:8000",
        skills=[{"id": "cool", "name": "Cool Skill", "description": "..."}],
    ),
    executor=MyCoolExecutor(),
)

server.listen(port=8000)

server.app exposes the raw Starlette ASGI app if you need to mount it under an existing FastAPI application:

fastapi_app.mount("/", server.app)

Agent card helpers

from web42_auth.a2a import build_agent_card, build_agent_card_security, AgentCardOptions

card = build_agent_card(AgentCardOptions(
    name="My Agent",
    description="...",
    base_url="https://my-agent.example.com",
))
# Returns a dict compatible with a2a.types.AgentCard

security = build_agent_card_security()
# Returns {"securitySchemes": {...}, "security": [...]}

AP2 Payments

Build and parse AP2 payment mandates for agent commerce.

from web42_auth import (
    build_cart_mandate,
    build_cart_mandate_data_part,
    build_cart_mandate_artifact,
    is_cart_mandate_part,
    is_payment_mandate_part,
    parse_cart_mandate,
    parse_payment_mandate,
    verify_payment,
    async_verify_payment,
)

Types

Building a CartMandate (merchant agents)

from web42_auth import build_cart_mandate, build_cart_mandate_data_part, AP2Amount, DisplayItem

cart = build_cart_mandate(
    order_id="order_latte_456",
    items=[
        DisplayItem(label="Iced Latte", amount=AP2Amount(currency="USD", value=4.50)),
        DisplayItem(label="Tax", amount=AP2Amount(currency="USD", value=0.45)),
    ],
    total=DisplayItem(label="Total", amount=AP2Amount(currency="USD", value=4.95)),
    merchant_signature="sig_starbucks_456",
)

data_part = build_cart_mandate_data_part(cart)

Parsing mandates (shopping agents)

from web42_auth import is_payment_mandate_part, parse_payment_mandate

for part in message["parts"]:
    if is_payment_mandate_part(part):
        mandate = parse_payment_mandate(part)
        print(mandate.user_authorization)  # JWT token

Verifying payment (merchant agents)

Sync:

from web42_auth import Web42Client, verify_payment

client = Web42Client(
    client_id="...",
    client_secret="...",
)

result = verify_payment(client, payment_token, "order_latte_456")
if result.valid:
    print(f"Verified: ${result.amount.value} from {result.payer_id}")

Async:

from web42_auth import AsyncWeb42Client, async_verify_payment

client = AsyncWeb42Client(...)
result = await async_verify_payment(client, payment_token, "order_latte_456")