Service Provider Guide

Guide for service providers to accept payments from Kite Agent Passport agents via x402 or MPP.

Kite Agent Passport can pay any service that implements one of two open payment protocols:

• x402 — HTTP 402-based payment protocol with on-chain settlement

• MPP (Machine Payments Protocol) — an open standard by Stripe and Tempo for machine-to-machine payments (mpp.dev)

If your service already speaks either protocol, Passport agents can pay you today. If you are starting fresh, this guide walks through both options.

We encourage deploying on Kite chain for the fastest settlement and tightest integration with Passport.

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How Passport Pays Your Service

1. An agent calls your service endpoint.

2. Your service returns 402 Payment Required with payment terms.

3. The Passport agent resolves payment using the user's approved spending session.

4. Your service receives proof of payment, verifies it, and delivers the response.

The specifics of step 2–4 depend on which protocol you implement.

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Option 1: Accept Payments via x402

x402 uses HTTP 402 responses to negotiate on-chain payments between agents and services.

Payment Flow

Payment Flow

1. Your service returns a 402 Payment Required response with payment details.

2. The Passport agent obtains a signed payment authorization from the user's session.

3. The agent resends the request with the X-Payment header.

4. You verify the payment token and call a facilitator to settle on-chain.

5. The facilitator executes the transfer to your wallet.

6. You deliver the service response.

Sample Service: Weather API (Testnet)

Weather Service (Testnet): https://x402.dev.gokite.ai/api/weather

Call it without payment:

curl https://x402.dev.gokite.ai/api/weather?location=San%20Francisco

Response (402 Payment Required):

{
  "error": "X-PAYMENT header is required",
  "accepts": [{
    "scheme": "gokite-aa",
    "network": "kite-testnet",
    "maxAmountRequired": "1000000000000000000",
    "resource": "https://localhost:8099/api/weather",
    "description": "Weather API - Public endpoint with query params",
    "mimeType": "application/json",
    "outputSchema": {
      "input": {
        "discoverable": true,
        "method": "GET",
        "queryParams": {
          "location": {"description": "City name or coordinates", "required": true, "type": "string"},
          "units": {"default": "metric", "enum": ["metric", "imperial"], "type": "string"}
        },
        "type": "http"
      },
      "output": {
        "properties": {
          "conditions": {"description": "Weather conditions", "type": "string"},
          "humidity": {"description": "Humidity percentage", "type": "number"},
          "temperature": {"description": "Current temperature", "type": "number"}
        },
        "required": ["temperature", "conditions"],
        "type": "object"
      }
    },
    "payTo": "0x4A50DCA63d541372ad36E5A36F1D542d51164F19",
    "maxTimeoutSeconds": 300,
    "asset": "0x0fF5393387ad2f9f691FD6Fd28e07E3969e27e63",
    "extra": null,
    "merchantName": "Weather Service"
  }],
  "x402Version": 1
}

Key Response Fields:

Field	Description	Example
scheme	Payment scheme	gokite-aa
network	Target network	kite-testnet
maxAmountRequired	Maximum payment amount (in wei)	1000000000000000000 (1 token)
asset	Token contract address	0x0fF5393387ad2f9f691FD6Fd28e07E3969e27e63
payTo	Your service wallet address	0x4A50DCA63d541372ad36E5A36F1D542d51164F19
maxTimeoutSeconds	Payment timeout	300
merchantName	Your service name	Weather Service
outputSchema	API input/output specification	(see above)

Kite Testnet Payment Token

For testnet services on Kite, use this token:

Token Address: 0x0fF5393387ad2f9f691FD6Fd28e07E3969e27e63

Token Details: https://testnet.kitescan.ai/token/0x0fF5393387ad2f9f691FD6Fd28e07E3969e27e63

Kite Facilitator

Kite works with any x402-compatible facilitator. The recommended facilitator for Kite chain:

Property	Value
Service	Pieverse Facilitator
Version	2.0.0
Base URL	https://facilitator.pieverse.io
Documentation	https://facilitator.pieverse.io/

Kite Testnet Facilitator Address:

0x12343e649e6b2b2b77649DFAb88f103c02F3C78b

API Endpoints:

Endpoint	Method	Description
/v2/verify	POST	Verify payment signature
/v2/settle	POST	Settle payment (execute on-chain)

The facilitator handles on-chain execution. Once payment is authorized, it calls transferWithAuthorization and transfers funds directly to your payee address.

Implementing x402 in Your Service

Step 1: Return 402 Payment Required

When a request arrives without valid payment, return a 402 with your payment terms:

{
  "error": "X-PAYMENT header is required",
  "accepts": [{
    "scheme": "gokite-aa",
    "network": "kite-testnet",
    "maxAmountRequired": "1000000000000000000",
    "resource": "https://your-service.com/api/endpoint",
    "description": "Your API - Description of your service",
    "mimeType": "application/json",
    "outputSchema": {
      "input": {
        "discoverable": true,
        "method": "GET",
        "queryParams": {
          "param1": {"description": "Parameter description", "required": true, "type": "string"}
        },
        "type": "http"
      },
      "output": {
        "properties": {
          "result": {"description": "Result description", "type": "string"}
        },
        "required": ["result"],
        "type": "object"
      }
    },
    "payTo": "0xYourServiceWalletAddress",
    "maxTimeoutSeconds": 300,
    "asset": "0x0fF5393387ad2f9f691FD6Fd28e07E3969e27e63",
    "extra": null,
    "merchantName": "Your Service Name"
  }],
  "x402Version": 1
}

Step 2: Receive and Verify the Payment Token

The agent resends the request with an X-Payment header containing a base64-encoded authorization:

curl -H "X-PAYMENT: eyJhdXRob3JpemF0aW9uIjp7..." \
  https://your-service.com/api/endpoint

Step 3: Settle via Facilitator

curl -X POST https://facilitator.pieverse.io/v2/settle \
  -H "Content-Type: application/json" \
  -d '{
    "authorization": {...},
    "signature": "0x...",
    "network": "kite-testnet"
  }'

Step 4: After confirming settlement, deliver your service response.

x402 Resources

• x402 Protocol Specification: https://docs.x402.org/introduction

• Pieverse Facilitator Docs: https://facilitator.pieverse.io/

• Kite x402 Reference Implementation: https://github.com/gokite-ai/x402

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Option 2: Accept Payments via MPP

MPP (Machine Payments Protocol) is an open standard co-authored by Stripe and Tempo. It extends the HTTP 402 pattern with support for multiple payment methods, session-based billing, and IETF standardization.

Payment Flow

1. Agent requests a resource from your service.

2. Your service responds with a 402 challenge containing payment terms.

3. The agent submits a credential (proof of payment).

4. Your service verifies the credential, returns a receipt, and delivers the resource.

Key Differences from x402

	x402	MPP
Payment methods	On-chain stablecoins	Stablecoins, fiat (Stripe), and more
Settlement	Via facilitator on-chain	Via Stripe or supported payment networks
Transport	HTTP headers (X-Payment)	HTTP, JSON-RPC, WebSocket
Session support	Via Passport spending sessions	Built-in payment channels

Getting Started with MPP

• MPP Specification: mpp.dev

• Stripe MPP Blog: stripe.com/blog/machine-payments-protocol

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Testing Your Integration

1. Set up a Passport account following the Introduction.

2. Fund the account with testnet tokens using the faucet.

3. Create an agent and approve a spending session.

4. Point the agent at your service endpoint.

5. Verify your service returns the correct 402 response.

6. Confirm payment is processed and your service delivers the response.

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Next Steps

1. Pick your protocol — x402 for on-chain payments on Kite, or MPP for multi-method support.

2. Set up a service wallet on Kite chain (for x402) or connect Stripe (for MPP).

3. Implement 402 responses in your service.

4. Test with Passport — follow the Introduction to create an agent and pay your service.

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Need help? Open an issue or contact the Kite team.