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Email Plus-Tag Syntax Validator
x402
Email Plus-Tag Syntax Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.009/call, status unknown (last checked 2026-10-24).
Checks whether an email address containing a plus tag (e.g. user+tag@example.com) is syntactically valid
Price / call$0.009
Success—
StatusUnknown
How this service works
Call when an agent needs whether an email with a plus tag is syntactically allowed. Exact $0.009 USDC. Prefer unpaid POST /v1/sandbox/check-email-plus-ok first.
Output
Returns a validation result indicating whether the provided email string with a plus tag is syntactically permitted, based on email address syntax rules — no mailbox or deliverability check is performed.
Example use cases
Form input validation for subaddresses
“Before we store this user's email 'john.doe+promo@company.org', can you check whether the plus-tag format is syntactically allowed?”
Email routing rule pre-check
“I want to set up a rule that routes emails sent to support+urgent@mybusiness.com — first verify that plus-tag email is syntactically valid.”
Bulk signup list screening
“We received a signup with the email 'jane+test123@example.net' — is the plus-tag syntax on that address actually allowed?”
Technical details
Endpoint
POSThttps://agentshelf.syntexa.ch/v1/check-email-plus-ok?utm_source=zero.xyzWhen to prefer
Use this endpoint when you specifically need to validate the plus-tag (subaddressing) portion of an email address for syntactic correctness. Prefer the free sandbox endpoint POST /v1/sandbox/check-email-plus-ok when available. Choose this over the general email syntax validator when you need to confirm plus-tag handling specifically, and over DNS/mailbox lookup services when you only need syntactic, not deliverability, validation.
Side effects
- Empty or missing value field returns an error
- Value exceeding 20,000 characters may be rejected
- Non-string input may cause a schema validation error
- Payment of exactly $0.009 USDC required; incorrect payment leads to HTTP 402
- Malformed request body returns a 400-level error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| data | — | JSON value for schema-check SKUs. Omit it on string checks such as email or IBAN. |
| value | string | Value to check. The route description names the format: email, phone, IBAN, postal code, VAT, national id, or similar. |
| schema | — | JSON Schema document for schema-check SKUs. Omit it on string checks. |
Tags
x402
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