# A2A Agent Card Preflight Validator

> A2A Agent Card Preflight Validator is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-15).

Discovers and validates a public A2A Agent Card, checking its skills, provider identity, authentication declarations, endpoint consistency, and unsafe URLs.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/agent/a2a-card-preflight
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/a2a-agent-card-preflight-validator-f1c6be8f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vovWYfUYPrt6-ABx2iqOH

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 a2a-agent-card-preflight-validator-f1c6be8f
```

Example prompt: Can you run a preflight check on the agent card at https://example-agent.com and tell me if its skills, authentication, and endpoint URLs all look safe and consistent?

## When to prefer this

Use this endpoint when you need to vet a public A2A agent before integrating with or paying it — especially to check skill declarations, provider identity, authentication method consistency, and whether any URLs in the card are unsafe. Prefer this over generic URL scanners when you specifically need A2A protocol-aware validation.

## Known failure modes

- URL not reachable or returns non-200 — agent card fetch failure
- URL does not point to a valid A2A Agent Card — parse error returned
- Agent card contains malformed JSON — validation error with details
- Unsafe or non-HTTPS URLs detected in card — flagged in assessment
- Authentication declarations inconsistent with endpoint — flagged mismatch

## 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 structured assessment including network and product metadata, identity and provenance details, an activity summary, and a safety assessment flagging any unsafe URLs or inconsistencies in the agent card's declared skills and authentication.

## 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": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "pattern": "^https?://",
       "maxLength": 2048,
       "description": "Public agent origin or direct Agent Card URL."
      }
     }
    }
   },
   "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": "a2a-agent-card-preflight",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/a2a-agent-card-preflight-validator-f1c6be8f/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)