# A2A Agent Card Validator

> A2A Agent Card Validator is a paid API for AI agents from agent.halowerk.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-13).

Validates an Agent Card document against the A2A convention, returning findings categorized by severity (error, warning, info) covering required fields, URL format, skill definitions, and security schemes.

## Facts

- Endpoint: POST https://agent.halowerk.com/v1/a2a-card-validate
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/a2a-agent-card-validator-4265818f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_kNE7ytbDxHRSvScHDPVpo

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-validator-4265818f -d '<json body>'
```

Example prompt: Check my A2A agent card document for compliance issues — I need to know if it has any errors that make it unusable, warnings where consuming agents might have to guess, or missing recommended fields.

## When to prefer this

Use this endpoint when you need to verify that an Agent Card document strictly conforms to the A2A interoperability convention before publishing or sharing it. Prefer it over manual review when you need machine-readable, severity-graded findings covering field presence, URL format, skill schema completeness, unique skill IDs, and security scheme correctness in a single call.

## Known failure modes

- Malformed JSON input returns a parse error before validation begins
- Agent card missing the outer wrapper structure may produce unexpected findings
- Very large or deeply nested cards may exceed payload limits
- Unknown or future A2A spec fields not yet recognized by the validator may be silently ignored
- Payment failure (x402) if USDC balance is insufficient

## How this service works

Validates an Agent Card document against the A2A convention and returns findings by severity: error (the card is unusable as published), warning (works, but a consuming agent will guess), info (recommended field absent). Checked: the required fields name, description, url, version, capabilities and skills; that url is absolute and https; that every skill carries id, name, description and tags and that skill ids are unique; that declared securitySchemes use a known type and that every entry in…

## Output

A structured report of validation findings grouped into three severity levels: errors (card is unusable as published, e.g. missing required fields like name, description, url, version, capabilities, or skills; non-absolute or non-HTTPS url), warnings (card works but consuming agents will have to guess), and info (recommended but absent fields). Each finding identifies the specific field or skill at issue.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "card": {
   "type": "object",
   "description": "The Agent Card document as JSON."
  },
  "strict": {
   "type": "boolean",
   "default": false,
   "description": "If true, recommended-field findings count as warnings and lower the verdict."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/a2a-agent-card-validator-4265818f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent.halowerk.com](https://www.zero.xyz/host/agent.halowerk.com/llms.txt)