# SignGate x402 Sumsub Proof-of-Address Evidence Preflight

> SignGate x402 Sumsub Proof-of-Address Evidence Preflight is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-14).

Validates a Sumsub applicant's proof-of-address evidence and computes a risk score before an AI agent proceeds with an x402-gated purchase.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/sumsub/poa-evidence
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signgate-x402-sumsub-proof-of-address-evidence-preflight-8b5ddee0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_mPY9qdGpoQrNHdT0ZWZ6w

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability signgate-x402-sumsub-proof-of-address-evidence-preflight-8b5ddee0
```

Example prompt: Before my agent buys that x402-gated dataset, run a proof-of-address preflight on Sumsub applicant ID 'app-7f3a9b2c' in jurisdiction US and tell me the risk score and any compliance flags.

## When to prefer this

Use this endpoint when an AI agent needs to perform a lightweight, per-call compliance preflight specifically against Sumsub proof-of-address evidence on the Base network (eip155:8453) before committing to an x402 micropayment. Prefer it over general KYC endpoints when the product category is 'sumsub-poa-evidence' and you need a structured risk score and flags rather than a binary pass/fail.

## Known failure modes

- Missing or malformed applicant_id returns a validation error
- Invalid jurisdiction code (not ISO-3166 two-letter uppercase) causes a 400 error
- Unknown or unregistered Sumsub applicant ID returns not-found or empty assessment
- Sumsub backend unavailability causes a 502/503 upstream error
- Payment not included or invalid x402 payment header returns 402 Payment Required

## How this service works

Machine-payable service intelligence for discovering, verifying, and monitoring identity, risk, authorization, execution-preflight, and evidence APIs before autonomous agents spend.

## Output

Returns a JSON object containing the EIP-155 network identifier (e.g. eip155:8453 for Base), the product name ('sumsub-poa-evidence'), and an assessment object with a risk_level string (e.g. 'low'), a numeric risk_score (0–100), and a flags array listing any compliance issues detected against the applicant's proof-of-address data.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "applicant_id"
     ],
     "properties": {
      "applicant_id": {
       "type": "string",
       "pattern": "^[A-Za-z0-9._:-]{1,128}$",
       "description": "Sumsub applicant id or sandbox fixture reference."
      },
      "jurisdiction": {
       "type": "string",
       "pattern": "^[A-Z]{2}$",
       "description": "ISO-3166 country code used by the policy gate."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "network": {
       "type": "string"
      },
      "product": {
       "type": "string"
      },
      "activity": {
       "type": "object"
      },
      "identity": {
       "type": "object"
      },
      "assessment": {
       "type": "object"
      },
      "provenance": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "sumsub-poa-evidence",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/signgate-x402-sumsub-proof-of-address-evidence-preflight-8b5ddee0/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-agent-preflight.bytoken2023.workers.dev](https://www.zero.xyz/host/base-agent-preflight.bytoken2023.workers.dev/llms.txt)