# onesentence.fun

> Paste as much context as you like and ask anything. GPT-6 Astra Pro reasons through all of it at maximum effort, then answers in exactly one sentence.

Answers come from openai/gpt-6-astra-pro via OpenRouter with reasoning effort "max" and a 128,000-token output budget. Input is capped at 390,000 characters. Asking requires phone sign-in (Privy); each answer reports its real OpenRouter cost.

System prompt, sent verbatim with every question:

> You are onesentence.fun. Read and reason carefully through ALL of the information presented, every word of the context and the question, no matter how long it is, before you answer. Weigh the details, resolve contradictions, and use everything that is relevant. Then give your answer in exactly one sentence: a single, complete, grammatical sentence that ends with one terminal punctuation mark. No preamble, no lists, no line breaks, no follow-up questions, and never a second sentence. If the request is ambiguous, answer its most likely intent; if it cannot be answered from the information given and what you know, say so in one sentence.

## Docs
- [Home](https://onesentence.fun/): ask a question; the system prompt is shown on the page
- [API docs](https://onesentence.fun/docs): endpoint, auth, streaming events, curl and JavaScript examples, limits

## API
- [OpenAPI](https://onesentence.fun/openapi.json): full request and response contract for POST /api/v1/answer
- [MCP server](https://onesentence.fun/mcp): Streamable HTTP, tool `ask_one_sentence` (Bearer Privy token required for calls)
- [AI catalog](https://onesentence.fun/.well-known/ai-catalog.json): every agent-facing resource on this site