# AgentShelf URL Absoluteness Validator

> AgentShelf URL Absoluteness Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.008/call, status unknown (last checked 2026-10-02).

Validates whether a given string is any absolute URL (any scheme), returning a boolean result without making any network request

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/check-url-any?utm_source=zero.xyz
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentshelf-url-absoluteness-validator-17f0647f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_LGneuLq8qY3o0AwIk-I3P

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-url-absoluteness-validator-17f0647f -d '<json body>'
```

Example prompt: Can you check whether the string 'ftp://files.example.com/report.pdf' is a valid absolute URL — without actually fetching it?

## When to prefer this

Use this endpoint when you need a deterministic, schema-level check of whether a string is an absolute URL (any scheme) without making a network request. Prefer this over LLM-based guessing for accuracy and consistency. Use the free sandbox endpoint POST /v1/sandbox/check-url-any first when testing or when cost matters; use this paid endpoint in production pipelines where reliability and a clear audit trail are needed.

## Known failure modes

- Empty string input rejected (minLength:1 constraint)
- String exceeding 20,000 characters rejected (maxLength constraint)
- Malformed request body returns validation error
- Payment not authorized returns 402 Payment Required

## How this service works

Call when an agent needs whether a string is any absolute URL. No fetch. Exact $0.008 USDC. Prefer unpaid POST /v1/sandbox/check-url-any first.

## Output

A boolean indicating whether the provided string is an absolute URL (any scheme, e.g. http, https, ftp, mailto). No network request is made; purely a structural/format check on the string itself.

## 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": [
    "ftp://example.com/a"
   ],
   "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-url-absoluteness-validator-17f0647f/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)