# agentshelf.syntexa.ch Email RFC Syntax Validator

> agentshelf.syntexa.ch Email RFC Syntax Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.007/call, status unknown (last checked 2026-10-02).

Validates whether an email address has syntactically valid RFC-compliant structure, without performing any mailbox or DNS lookup.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/check-email-rfc?utm_source=zero.xyz
- Price: $0.007/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentshelf-syntexa-ch-email-rfc-syntax-validator-14cc3d85
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_f6kvB1crR-mfRERIhTl25

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 agentshelf-syntexa-ch-email-rfc-syntax-validator-14cc3d85 -d '<json body>'
```

Example prompt: Can you check if 'user.name+tag@example.co.uk' is a syntactically valid email address according to RFC rules — just the format, no need to check if the mailbox exists.

## When to prefer this

Choose this endpoint when you need a fast, cheap, purely syntactic check of an email address format before storing, routing, or acting on it — and you do not need to verify mailbox existence or deliverability. Prefer the free sandbox variant (/v1/sandbox/check-email-rfc) for testing. Use this paid endpoint only in production flows where sandbox access is unavailable or quota is exhausted.

## Known failure modes

- Empty or missing value field returns an error
- Value exceeding 20,000 character limit rejected
- Malformed JSON request body results in 4xx error
- Payment of exactly $0.007 USDC not supplied triggers 402 Payment Required
- Sandbox endpoint (/v1/sandbox/check-email-rfc) should be tried first to avoid unnecessary charges

## How this service works

Call when an agent needs whether an email address has a usable syntax. No mailbox lookup. Exact $0.007 USDC. Prefer unpaid POST /v1/sandbox/check-email-rfc first.

## Output

Returns a boolean or structured result indicating whether the submitted email address string conforms to RFC email syntax rules. No mailbox existence, DNS resolution, or SMTP check is performed — purely structural/syntactic validation.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "data": {
   "description": "JSON value for schema-check SKUs. Omit it on string checks such as email or IBAN."
  },
  "value": {
   "type": "string",
   "examples": [
    "agent@example.com"
   ],
   "maxLength": 20000,
   "minLength": 1,
   "description": "Value to check. The route description names the format: email, phone, IBAN, postal code, VAT, national id, or similar."
  },
  "schema": {
   "description": "JSON Schema document for schema-check SKUs. Omit it on string checks."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentshelf-syntexa-ch-email-rfc-syntax-validator-14cc3d85/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)