Building Payment-Ready AI Agents from Day 1

1. User Consent is Non-Negotiable

PSPs lose chargebacks when users say "I didn't authorize this." Build consent into your architecture from the start.

✓ Every agent action = explicit user approval OR pre-configured rule

✓ Store consent receipts (RFC 9600): timestamp, user_id, action, amount, IP

✓ Retention: 18 months (Visa dispute window)

2. Human-in-Loop for High-Value Transactions

Don't make your agent fully autonomous. Build a 'Trust Threshold' system.

✓ Config: user.trust_threshold (default: $100)

✓ If transaction > threshold: Require explicit approval

✓ If transaction < threshold: Auto-execute (but log consent)

3. Audit Trails for Every Decision

PSPs ask: "Why did your agent make THIS purchase?" You need to show them.

✓ Log: agent reasoning, alternatives considered, why this was chosen

✓ Store in: agent_decisions table (action_id, reasoning, alternatives_json)

✓ Use for: Chargeback disputes, PSP audits, user transparency

4. Rate Limiting & Velocity Controls

Bot-like behavior triggers fraud alerts. Build rate limits into your agent's execution layer.

✓ Per-user limits: Max 50 transactions/day, max $5,000/day

✓ Per-agent limits: Max 1,000 transactions/hour

✓ Implement with: Redis rate limiting (sliding window)

5. Identity Verification (Visa TAP)

Build agent identity into your HTTP layer from the start.

✓ Generate ES256 key pair on first deployment

✓ Middleware: Sign every outbound payment request (RFC 9421)

✓ Publish public key: yourdomain.com/.well-known/jwks.json

1. Agent Framework

Lang Graph (Python), CrewAI, or AutoGPT. Built-in state management + tool execution tracking.

2. Consent Management

consent-receipt library (npm) or build your own. PostgreSQL storage. JSON with HMAC signature.

3. Rate Limiting

Redis + rate-limiter-flexible (Node.js) or slowapi (Python). Sliding window pattern.

4. HTTP Signing (Visa TAP)

http-message-signatures library. Store keys in AWS Secrets Manager or Google Secret Manager.

5. Audit Logging

Winston (Node.js) or Loguru (Python). Store in BigQuery or PostgreSQL. 18-month retention.

agent_transactions

id, user_id, agent_id, amount, currency, status,
consent_receipt_id, created_at
// Indexes: user_id, created_at
// Retention: 18 months

consent_receipts

id, user_id, action_type, action_details_json,
amount, user_ip, timestamp, signature
// Purpose: Prove user authorized transaction
// Retention: 18 months (Visa requirement)

agent_decisions

id, transaction_id, reasoning_text,
alternatives_json, chosen_option, confidence_score
// Purpose: Audit trail for 'why this action?'
// Retention: 18 months

rate_limit_events

id, user_id, action_type, count,
window_start, window_end
// Purpose: Track velocity, detect abuse
// Retention: 90 days

✅ Architecture

✅ Database

✅ Security

✅ Compliance