Architecture

Pincer enables a seamless value exchange between AI agents and service providers.

Protocol Flow

The core interaction follows the Request-Pay-Verify-Rebate cycle.

sequenceDiagram
    participant User
    participant Agent as AI Agent (Client)
    participant Server as Resource Server
    participant Blockchain
    participant Sponsor

    User->>Agent: Request "Best Pizza NYC"
    Agent->>Server: GET /recommendations
    Server-->>Agent: 402 Payment Required
    Note right of Server: x402 Header: <br/>"pay 0.01 USDC to addr..."

    Agent->>Blockchain: Sign & Broadcast Tx
    Blockchain-->>Agent: Confirmed

    Agent->>Server: Retry Request + Proof
    Server->>Blockchain: Verify Transaction
    Blockchain-->>Server: Defines Success

    Server-->>Agent: 200 OK + Data
    Note right of Server: Returns Recommendations<br/>+ Sponsor Rebate Offer

    rect rgb(240, 248, 255)
    Note over Sponsor, Blockchain: Async / Post-Process
    Sponsor->>Blockchain: Detects Tx & Refunds User
    Blockchain-->>User: +0.01 USDC (Rebate)
    end

Key Components

1. Resource Server (x402-server)

The gatekeeper. It intercepts requests, checks for valid payment headers, and issues 402 challenges if payment is missing. In Pincer, this is wrapped by PincerResourceServer for simpler integration.

2. Facilitator (Verified by Pincer)

An on-chain or off-chain entity that verifies the payment occurred. Pincer acts as a facilitator, indexing blockchain events to confirm transactions instantly. The facilitator logic has been professionally audited (Link to Report).

3. Sponsors

Third-party entities (like Restaurants, Brands) that configure "Campaigns". If a user's request matches a campaign criteria (e.g., "User paid for Pizza search"), the sponsor triggers a rebate transaction to the user's wallet.