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Integrate the Predicate API into your backend to evaluate users against your configured policy. The API returns a compliance result and a signed attestation.
1

Backend Integration

Call the Predicate API from your server using your API key.
2

Handle the Response

Use is_compliant to gate access in your application.

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Backend Integration

Store your API key on the server and call the Predicate API. Use the verification_hash from your project and the user’s wallet address. 
import express from 'express';

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

app.post('/api/compliance/check', async (req, res) => {
  const { userAddress } = req.body;

  const response = await fetch('https://api.predicate.io/v2/attestation', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'x-api-key': process.env.PREDICATE_API_KEY,
    },
    body: JSON.stringify({
      verification_hash: process.env.PREDICATE_VERIFICATION_HASH,
      from: userAddress,
      chain: 'ethereum',
    }),
  });

  const result = await response.json();

  if (!result.is_compliant) {
    return res.status(403).json({
      error: 'User not compliant',
      policy: result.policy_name,
      reason: result.reason, // may include code and message from the policy
    });
  }

  // User is compliant — proceed with your business logic
  res.json({ compliant: true });
});

​
Request Parameters

FieldRequiredDescription
verification_hashYesYour project identifier from the dashboard
fromYesThe user’s wallet address to evaluate
chainYesChain name (e.g., ethereum, base, arbitrum)

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Response

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Compliant

{
  "policy_id": "policy_abc123",
  "policy_name": "Standard AML Policy",
  "verification_hash": "x-abc123def456",
  "is_compliant": true,
  "attestation": {
    "uuid": "550e8400-e29b-41d4-a716-446655440000",
    "expiration": 1696640400,
    "attester": "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266",
    "signature": "0x1b2c3d4e5f..."
  }
}

​
Non-Compliant

Some policies include a reason object on non-compliant responses with details about why the evaluation failed. Both the code and message values are fully customizable when authoring a policy. 
{
  "policy_id": "x-dev-trm-risk-abc123",
  "policy_name": "TRM Risk Score",
  "verification_hash": "x-abc123def456",
  "is_compliant": false,
  "attestation": {
    "uuid": "550e8400-e29b-41d4-a716-446655440000",
    "expiration": 0,
    "attester": "",
    "signature": ""
  },
  "reason": {
    "code": "trm_high_risk",
    "message": "TRM risk score for this wallet is 10 which exceeds the maximum allowed of 7"
  }
}
FieldDescription
is_compliantWhether the user passed the policy evaluation
policy_nameName of the policy that was evaluated
attestationSigned attestation (used for onchain enforcement in Phase 2)
reasonOptional object on non-compliant responses. Contains code (machine-readable) and message (human-readable) fields defined by the policy.

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Supported Chains

ChainValue
Ethereumethereum
Basebase
Arbitrumarbitrum
Hyperliquidhyperliquid
Plumeplume
BSCbsc
Plasmaplasma
Worldworldchain
Sepoliasepolia
Base Sepoliabase_sepolia
Solanasolana
MegaETHmegaeth
MegaETH Testnetmegaeth_testnet

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Next Steps

Your offchain integration is complete. Your application can now evaluate compliance for any user. When you’re ready to enforce compliance at the smart contract level, continue to Onchain Enforcement.