# Agent Payment Guard — x402 Server Trust Assessment

> Agent Payment Guard — x402 Server Trust Assessment is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Returns a risk score, risk level, and flags for a given x402 payment server URL to help AI agents decide whether to trust and pay it.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/x402/server-trust
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-payment-guard-x402-server-trust-assessment-e902c36d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KeKzIMBJU3i_ATHrMI5eK

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 agent-payment-guard-x402-server-trust-assessment-e902c36d
```

Example prompt: Before my agent pays, can you check the trust and risk score for the x402 server at https://api.example.com — the marketplace says it has 150 transactions, 40 unique buyers, 12000.50 USDC volume, it's on Base, and the last payment was seen 2 hours ago?

## When to prefer this

Use this endpoint when an AI agent is about to make an autonomous x402 payment and needs a pre-flight risk assessment of the target server. Prefer this over generic URL reputation services because it is x402-protocol-aware, understands seller addresses, on-chain transaction counts, and USDC volume signals specific to the x402 ecosystem.

## Known failure modes

- Missing required server_url parameter returns a validation error
- Invalid seller address format (not 0x + 40 hex chars) causes a 400 error
- Unreachable or unknown server_url may return a higher risk_score or empty provenance
- Rate limiting or quota exhaustion returns a 429 or payment-required response
- Malformed numeric query params (txns, buyers, volume_usdc) fail schema validation

## 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

A JSON object containing the network (e.g. eip155:8453), product identifier ('x402-server-trust'), and an assessment object with risk_score (numeric), risk_level (e.g. 'low', 'medium', 'high'), and a flags array listing any detected risk signals, plus optional activity, identity, and provenance objects.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "x402-server-trust",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-payment-guard-x402-server-trust-assessment-e902c36d/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)