feat: add AgentPay x402 payment tools for ADK agents #107
Description
Summary
Add AgentPay payment tools that enable ADK agents to make autonomous HTTP payments using the x402 protocol (HTTP 402 Payment Required → automatic on-chain payment → retry).
Motivation
AI agents increasingly need to call paid APIs and make micropayments autonomously. The x402 protocol provides a standard machine-to-machine payment flow. AgentPay provides non-custodial smart contract wallets with on-chain spend limits that protect against runaway agent behavior — essential for safe autonomous payment.
This was previously submitted to google/adk-python (PR #4937), where reviewer @rohityan correctly redirected it here with the note: "We highly recommend releasing the feature as a standalone package that we will then share through https://google.github.io/adk-docs/integrations/"
The standalone packages already exist on npm:
agentpay-mcp— MCP server (patent pending)agentwallet-sdk— core SDK
Proposed Tools
| Tool | Description |
|---|---|
fetch_paid_api |
Fetch a URL; auto-pay x402 HTTP 402 challenge if needed |
get_wallet_info |
Return wallet address, USDC balance, spend limits, remaining allowance |
check_spend_limit |
Pre-check whether a payment is within on-chain spend limits |
send_payment |
Send USDC directly to an address within spend policy |
Technical Details
- Chain: Base (live), multi-chain coming
- Token: USDC
- Protocol: x402 / HTTP 402
- Non-custodial: smart contract wallet owned via NFT
- Spend limits: enforced on-chain before any transaction is signed
- Transport: MCP stdio subprocess (standard MCP protocol)
Files to be Added
contributing/tools/agentpay/README.md
src/google/adk_community/tools/__init__.py
src/google/adk_community/tools/agentpay/__init__.py
src/google/adk_community/tools/agentpay/agentpay_tools.py
tests/unittests/tools/__init__.py
tests/unittests/tools/agentpay/__init__.py
tests/unittests/tools/agentpay/test_agentpay_tools.py