{"uid":"cap_rHkU9MulIr0T3QroXiQQi","slug":"fastapi-online-openapi-spec-generator-704a7e12","name":"fastapi.online — OpenAPI Spec Generator","description":"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.","url":"https://api.fastapi.online/generate-openapi","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"description":{"type":"string","maxLength":2000,"minLength":2,"description":"the API to document"}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_gEDN9JqTtgNBiefb7yqhM","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Generates an OpenAPI specification document from a plain-text description of an API","exampleAgentPrompt":"Generate an OpenAPI spec for a REST API that lets users create, read, update, and delete todo items, with endpoints for listing all todos, fetching a single todo by ID, and marking a todo as complete.","exampleUseCases":[{"title":"Scaffold API spec from idea","prompt":"I have an idea for a simple weather API that takes a city name and returns current temperature, humidity, and a 5-day forecast — can you generate a proper OpenAPI spec for it?"},{"title":"Document internal microservice","prompt":"Generate an OpenAPI specification for our user authentication service — it has endpoints for signup, login, logout, password reset, and token refresh, all using JWT."},{"title":"Prototype API for a hackathon","prompt":"I'm building a recipe recommendation API for a hackathon — it takes dietary preferences and a list of ingredients and returns matching recipes with instructions. Can you produce an OpenAPI 3.0 spec for it?"}],"resultDescription":"An OpenAPI specification document (likely JSON or YAML) describing the endpoints, request/response schemas, parameters, and structure of the API based on the plain-text description provided.","failureModes":["Description too short (below 2 character minimum) returns a validation error","Description exceeds 2000 character maximum and is rejected","Vague or ambiguous descriptions may produce incomplete or generic specs","Payment failure (insufficient USDC) results in 402 response","Server unavailability results in timeout or 5xx error"],"whenToPreferThis":"Choose this endpoint when you need a quick, pay-per-call OpenAPI spec generation without signing up for a full documentation platform. Ideal for prototyping, hackathons, or automating API documentation workflows where you have a natural language description of an API and need a structured spec output at low cost.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T00:44:43.031Z","isFirstParty":false}