OPA_POLICIES.md

Open Policy Agent (OPA) Policies

This document explains how to set up and use OPA policies with the Payment Agent.

Prerequisites

• Install OPA: https://www.openpolicyagent.org/docs/latest/#running-opa

Loading Policies

1. Start OPA server:

   opa run -s

2. Load the policy file:

   curl -X PUT http://localhost:8181/v1/policies/payments --data-binary @example_policy.rego

Testing Policies

You can test policies directly with OPA:

curl -X POST http://localhost:8181/v1/data/payments/allow \
  -H "Content-Type: application/json" \
  -d '{
    "input": {
      "purchase": {
        "amount": 500,
        "merchant": "valid_merchant",
        "mcc": "valid_mcc"
      }
    }
  }'

Policy Structure

The current example policy evaluates purchases based on:

• Amount limits (currently $1000)
• Blacklisted merchants
• Restricted MCC codes

Modify the policy according to your business requirements.

Integration with Payment Agent

The Payment Agent sends purchase requests to OPA for evaluation. The structure sent to OPA is:

{
  "input": {
    "purchase": {
      "userId": "user123",
      "agentId": "agent456",
      "amount": 100.0,
      "merchant": "some_merchant",
      "mcc": "some_mcc"
    }
  }
}

OPA responds with a boolean allow/deny decision that the Payment Agent uses to determine whether to proceed with the purchase.