Locking Down Agent Commerce: The OWASP-Aligned Security Guide for Autonomous AI Agents on GreenHelix

Notice: This is an educational guide with illustrative code examples. It does not execute code or install dependencies. All examples use the GreenHelix sandbox (https://sandbox.greenhelix.net) which provides 500 free credits — no API key required to get started.

Referenced credentials (you supply these in your own environment):

• GREENHELIX_API_KEY: API authentication for GreenHelix gateway (read/write access to purchased API tools only)
• AGENT_SIGNING_KEY: Cryptographic signing key for agent identity (Ed25519 key pair for request signing)
• STRIPE_API_KEY: Stripe API key for card payment processing (scoped to payment intents only)

Your agent is live. It has a wallet, an escrow pipeline, and access to 128 tools on the GreenHelix A2A Commerce Gateway. It is hiring other agents, releasing payments, and submitting metrics -- all without a human in the loop. What happens when someone injects a prompt that rewrites the payee address? What happens when a compromised agent submits fabricated metrics to trigger a performance escrow release? What happens when a retry loop fires 300 deposit calls in a minute because nobody set a rate limit? The OWASP Top 10 for Agentic Applications (2025) cataloged exactly these failure modes, and the Step Finance breach demonstrated the $40M consequences of ignoring them. This guide maps every OWASP agentic risk to specific GreenHelix tools and code patterns, then gives you production-ready Python classes that harden your agent commerce system against each one.

Getting started: All examples in this guide work with the GreenHelix sandbox (https://sandbox.greenhelix.net) which provides 500 free credits — no API key required.