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fastapi.online — JSON Schema Generator
x402
fastapi.online — JSON Schema Generator is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-18).
Generates a JSON Schema definition from a provided JSON example or description string
Price / call$0.001
Success—
StatusUnknown
How this service works
Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding & crypto utilities, date/time calculators, geo/coordinate math, math & finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.
Output
Returns a JSON Schema document (typically a JSON object conforming to the JSON Schema specification) inferred from the provided JSON input, including type definitions, required fields, and property structures.
Example use cases
Auto-generate API request schema
“I have a sample JSON payload from our API — {"userId": "abc123", "amount": 49.99, "currency": "USD", "timestamp": "2024-01-01T00:00:00Z"} — can you generate a proper JSON Schema from it so I can use it for validation?”
Validate incoming webhook data
“I need a JSON Schema to validate webhook payloads that look like this: {"event": "order.created", "orderId": 1042, "items": [{"sku": "A1", "qty": 2}]}. Can you generate one from that example?”
Document data structure for teammates
“Here's a JSON config object we use internally: {"featureFlag": "dark_mode", "enabled": true, "rolloutPercentage": 50}. Generate a JSON Schema from it so I can share it as documentation with the team.”
Technical details
Endpoint
POSThttps://api.fastapi.online/json-schema-generate?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to programmatically derive a JSON Schema from an existing JSON example without manual schema authoring. It is ideal for developer automation workflows, API documentation generation, data validation setup, or when onboarding unfamiliar data structures. At $0.001 USDC per call with no signup required, it suits lightweight, pay-as-you-go agent pipelines that need schema generation as a utility step.
Side effects
- Empty or missing 'json' field returns a validation error
- Malformed or non-JSON string input may result in a parse error or unexpected schema
- Input exceeding 20,000 characters is rejected due to maxLength constraint
- Ambiguous or deeply nested JSON may produce an overly generic schema with 'any' types
- Payment failure via x402 protocol results in 402 response and no schema returned
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| json | string |
Tags
x402
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