The Dexter Facilitator

The Facilitator is the settlement engine that powers x402 payments. It verifies transactions, broadcasts to the blockchain, and sponsors fees.

Base URL: https://x402.dexter.cash

Supported Networks

Cross-chain bridging is also supported between Solana and Base via the bridge scheme.

V1 Compatibility: The facilitator also accepts legacy network strings (solana, solana-devnet, base, base-sepolia) for backward compatibility with v1 clients.

What Does It Do?

When an AI agent wants to pay for an API, the Facilitator:

1. Verifies the transaction meets policy requirements
2. Signs the transaction as fee payer (sponsors the transaction fee)
3. Broadcasts the transaction to the blockchain
4. Confirms settlement on-chain

Why Use a Facilitator?

Without a Facilitator

Every seller would need to:

• Run blockchain RPC nodes
• Implement transaction parsing and policy checks
• Handle priority fees
• Manage confirmation logic

With the Dexter Facilitator

• Zero infrastructure - We handle all blockchain complexity
• Fee sponsorship - We pay transaction fees so buyers don't need native tokens
• Policy enforcement - Prevents malicious transactions
• Multi-chain - Solana, Base, Polygon, Avalanche, and more from a single integration

Endpoints

GET /supported

Returns the supported scheme/network combos, fee payer addresses, and registered extensions.

Response:

{
  "kinds": [
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "extra": { "feePayer": "SOLANA_FEE_PAYER" }
    },
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "eip155:8453",
      "extra": {}
    },
    {
      "x402Version": 2,
      "scheme": "bridge",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "extra": {
        "bridgeDestinations": ["eip155:8453"],
        "bridgeFeePercent": 0.1
      }
    }
  ],
  "extensions": ["bazaar"],
  "signers": {
    "solana:*": ["SOLANA_FEE_PAYER"],
    "eip155:*": ["EVM_FEE_PAYER"],
    "*": ["SOLANA_FEE_PAYER", "EVM_FEE_PAYER"]
  }
}

POST /verify

Validates that a payment payload satisfies the given requirements.

Request:

{
  "paymentPayload": {
    "x402Version": 2,
    "resource": {
      "url": "https://api.dexter.cash/your/paid/route",
      "description": "Your paid resource",
      "mimeType": "application/json"
    },
    "accepted": {
      "scheme": "exact",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "asset": "SPL_MINT_ADDRESS",
      "amount": "10000",
      "payTo": "SELLER_WALLET",
      "maxTimeoutSeconds": 60,
      "extra": { "feePayer": "FEE_PAYER_ADDRESS" }
    },
    "payload": {
      "transaction": "BASE64_VERSIONED_TRANSACTION"
    }
  },
  "paymentRequirements": {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "asset": "SPL_MINT_ADDRESS",
    "amount": "10000",
    "payTo": "SELLER_WALLET",
    "maxTimeoutSeconds": 60
  }
}

Response (success):

{ "isValid": true, "payer": "PAYER_WALLET" }

Response (failure):

{
  "isValid": false,
  "invalidReason": "Amount below minimum",
  "invalidCode": "policy:amount_below_min"
}

POST /settle

Signs the transaction with the facilitator fee payer, submits it, and confirms it.

Request: Same shape as /verify.

Response (success):

{
  "success": true,
  "transaction": "TRANSACTION_SIGNATURE",
  "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
  "payer": "PAYER_WALLET"
}

Response (failure):

{
  "success": false,
  "transaction": "",
  "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
  "errorReason": "Asset not allowed",
  "errorCode": "policy:asset_not_allowed"
}

Sponsor Policy

Solana (SVM)

The facilitator only signs Solana transactions that satisfy all of the following:

Allowed programs:

• ComputeBudget
• SPL Token
• Token-2022
• Phantom Lighthouse

Disallowed:

• System program (no account creation / rent drain)
• Associated Token Account program

Transaction requirements:

• Exactly one SPL TransferChecked instruction
• VersionedTransaction only (legacy rejected)
• No Address Lookup Tables

Caps enforced:

• Max compute units (200,000)
• Max priority fee (100,000 microlamports/CU)
• Allowed assets (USDC by default)
• Min payment amount (0.01 USDC)

Base (EVM)

EVM transactions must be simple ERC-20 transfers to the seller's address. The facilitator validates the transfer amount and recipient match the payment requirements.

Policy Error Codes (Solana)

These policy:* codes are returned when a Solana transaction violates sponsor policy:

Backpressure Error Codes

These codes are returned when rate limits are exceeded:

Live Statistics

View real-time settlement volume, success rates, and network stats on the Ecosystem page →

Support

• Telegram: @DexterAISolBot
• Twitter: @dexteraisol