# x402 facilitator (/integration-guides/x402-facilitator)



This guide is for a facilitator that already accepts x402 payment requests and wants AgentTrust decisions before settlement.

## Integration points [#integration-points]

| Step | Facilitator action                    | AgentTrust call                   |
| ---- | ------------------------------------- | --------------------------------- |
| 1    | parse payer, payee, mint, and amount  | none                              |
| 2    | check policy                          | `POST /verify` or `gatePayment()` |
| 3    | return x402 denial or validation need | TrustGate header builder          |
| 4    | settle payment                        | single Solana transaction         |
| 5    | emit feedback                         | TrustGate `emit_feedback`         |

## Minimal Express mount [#minimal-express-mount]

```ts
import express from "express";
import { mountTrustGate } from "@agenttrust-sdk/trustgate/express";

const app = express();
app.use(express.json());

await mountTrustGate(app, {
  rpcUrl: process.env.SOLANA_RPC_URL!,
  facilitatorKeypair,
  defaultPolicyId: 1,
  network: "solana-devnet",
  atomicityEnforced: true,
});
```

## Verify request [#verify-request]

```http
POST /verify
Content-Type: application/json

{
  "payerAgentAsset": "payer-agent-asset-pubkey",
  "payeeAgentAsset": "payee-agent-asset-pubkey",
  "amount": "1000000",
  "mint": "mint-pubkey",
  "policyId": 1
}
```

## Denial response [#denial-response]

```http
HTTP/1.1 402 Payment Required
X-Payment-Network: solana-devnet
X-Agent-Trust-Decision: Deny
X-Payment-Required: denied
X-Payment-Reason-Code: 6
X-Payment-Reason-Name: CounterpartyTierBelowMin
```

## Validation response [#validation-response]

```http
HTTP/1.1 402 Payment Required
X-Payment-Network: solana-devnet
X-Agent-Trust-Decision: RequireValidation
X-Payment-Required: validation
X-Capability-Required: <32-byte-capability-hash>
```

## Settlement rule [#settlement-rule]

The facilitator must keep the policy gate, token transfer, and feedback emission in one Solana transaction once the settlement builder is wired. The SDK makes that requirement explicit with `atomicityEnforced: true`.

Source: `trustgate/server/src/x402.ts`, `trustgate/sdk/src/express.ts`.