Observer Protocol × Stripe MPP

The trust layer for Machine Payment Protocol (MPP). Add cryptographic agent reputation to any MPP/x402 seller in one middleware line.

The Problem

MPP solves machine payments. It doesn't solve machine identity.

When an agent sends an MPP payment, the receiving server gets paid. What it doesn't get is any verifiable answer to: has this agent paid reliably before? Is it a bot? Should I rate-limit it?

Observer Protocol closes that gap.

Quickstart

npm install @observer-protocol/sdk

const { ObserverClient } = require('@observer-protocol/sdk');
const observer = new ObserverClient();

// Add before your MPP/x402 payment handler
app.use('/api/*', observer.reputationMiddleware({ fallback: 'review' }));

// req.observerReputation.trust_tier      → "new" | "active" | "established" | "trusted"
// req.observerReputation.reputation_score → 0.0 – 1.0
// req.observerReputation.suggested_action → "accept" | "review" | "reject"

Reputation API (Live Now)

GET https://api.observerprotocol.org/observer/reputation/{agent_id}
GET https://api.observerprotocol.org/observer/reputation/wallet/{evm_address}

No API key required. Try it:

curl https://api.observerprotocol.org/observer/reputation/maxi-0001

Trust Tiers

Tier	Criteria	Suggested Action
unknown	No OP record	review
new	<10 events, <14 days	accept
active	10-99 events, 14+ days	accept
established	100+ events or 60+ days, multi-protocol	accept
trusted	500+ events, 180+ days, diversity >0.7	accept (premium)

Protocol Identifier

Use x402_stripe when attesting Stripe/MPP payments to track Stripe-specific activity separately.

Architecture

┌─────────────────────────────────────┐
│      OBSERVER PROTOCOL LAYER        │  ← "Can I trust this agent?"
└──────────────────┬──────────────────┘
                   │
┌──────────────────▼──────────────────┐
│      STRIPE MACHINE PAYMENTS / MPP  │  ← "Process this payment"
└──────────────────┬──────────────────┘
                   │
┌──────────────────▼──────────────────┐
│   Base (USDC) · Solana · Tempo      │  ← Payment rails
└─────────────────────────────────────┘

Files

• index.js — Node.js SDK + Express middleware
• observer_sdk.py — Python/FastAPI SDK
• X-OBSERVER-HEADERS.md — X-Observer header specification
• examples/stripe-x402-seller.js — Complete Stripe x402 seller example

Links

• Full quickstart: observerprotocol.org/quickstart-stripe
• Live demo: observerprotocol.org/demo
• API reference: observerprotocol.org/api
• Architecture: observerprotocol.org/architecture