# Singular Developer Documentation > Technical index for Singular's verified Chat Completions subset, routing controls, billing, integrations, limitations, and machine-payment handshakes. API origin: https://api.impossi.build OpenAI SDK base URL: https://api.impossi.build/v1 Documentation origin: https://singular.impossibuild.ai/docs Updated: 2026-08-10 Load the smallest relevant page set. Treat every compatibility surface independently and use the live API response as the final contract. ## Home Start from the live Singular contract and choose the documentation section that matches your task. - [Overview](https://singular.impossibuild.ai/docs): One API key, a live multi-provider model catalog, OpenAI-shaped chat, and optional machine-payment rails. Maturity: Stable. ## Tutorials Learn Singular by completing a working request from key claim through streaming. - [Tutorials](https://singular.impossibuild.ai/docs/tutorials): Follow a guided path from a funded key to a verified routed response and a working stream. Maturity: Informational. - [Quickstart](https://singular.impossibuild.ai/docs/quickstart): Claim a funded key, verify one routed response, pin a live model, and confirm streaming from a terminal. Maturity: Stable. ## How-to guides Complete a specific integration, key-management, application, or per-call payment task. - [How-to guides](https://singular.impossibuild.ai/docs/how-to-guides): Choose a practical procedure for authentication, clients, provider keys, the web app, or per-call payments. Maturity: Informational. - [Authenticate requests](https://singular.impossibuild.ai/docs/authentication): Send a Singular API key safely, manage its lifecycle, and handle the accountless payment exception. Maturity: Stable. - [Connect a client](https://singular.impossibuild.ai/docs/integrations): Connect tools that let you set an OpenAI-compatible base URL and use Chat Completions. Maturity: Informational. - [Attach provider keys](https://singular.impossibuild.ai/docs/byok): Attach or replace provider credentials without exposing them to the browser and choose when Singular may use them. Maturity: Limited. - [Use the chat app](https://singular.impossibuild.ai/docs/app/features): Start routed threads, compare models, organize work in Spaces, share results, and manage account controls. Maturity: Informational. - [x402](https://singular.impossibuild.ai/docs/payments/x402): Understand Singular's x402 v2 handshake, request binding, response headers, and current release gates. Maturity: Deployment gated. - [MPP](https://singular.impossibuild.ai/docs/payments/mpp): Use the HTTP Payment challenge flow and understand the Singular-specific USDC methods and chain requirements. Maturity: Deployment gated. ## Reference Find exact request fields, compatibility, routing, streams, billing, and limitations. - [Reference](https://singular.impossibuild.ai/docs/reference): Find exact endpoints, request fields, routing controls, streams, billing behavior, limitations, and agent-readable sources. Maturity: Informational. - [Chat Completions](https://singular.impossibuild.ai/docs/api/chat-completions): The stable data-plane contract, its supported parameters, response shape, and current compatibility boundaries. Maturity: Stable. - [Compatibility matrix](https://singular.impossibuild.ai/docs/api/compatibility): Know exactly which OpenAI, Anthropic, Gemini, and media-shaped routes are production-ready. Maturity: Informational. - [Routing controls](https://singular.impossibuild.ai/docs/routing-controls): Use fallback model lists, routing profiles, provider preferences, and the supported model suffixes. Maturity: Limited. - [Streaming & errors](https://singular.impossibuild.ai/docs/streaming-errors): Parse Singular's Chat Completions SSE stream correctly and retry only failures that can reasonably recover. Maturity: Stable. - [Billing & usage](https://singular.impossibuild.ai/docs/billing-usage): Understand the live retail price source, balance-backed requests, and the difference between authoritative totals and UI estimates. Maturity: Stable. - [Limitations](https://singular.impossibuild.ai/docs/limitations): What is implemented, what is partial, and which attractive-looking UI or route surfaces are not release-ready. Maturity: Informational. - [LLM-readable docs](https://singular.impossibuild.ai/docs/llm-discovery): Use the concise index for discovery and the full text bundle when a task genuinely needs the complete contract. Maturity: Informational. ## Explanation Understand model identity, automatic routing, fallbacks, and role-gated platform boundaries. - [Explanation](https://singular.impossibuild.ai/docs/explanation): Build a mental model of routing, model identity, provider fallbacks, and the boundary between public and role-gated surfaces. Maturity: Informational. - [How routing works](https://singular.impossibuild.ai/docs/models-routing): Understand the live catalog, explicit and automatic model selection, provider health, and fallback behavior. Maturity: Stable. - [Partner and operator roles](https://singular.impossibuild.ai/docs/platform/partners): Understand the role-gated commercial and control-plane surfaces without confusing them with the public model API. Maturity: Limited. ## Full corpus - [Complete technical documentation](https://singular.impossibuild.ai/docs/llms-full.txt): All pages concatenated as Markdown. - [Live retail pricing](https://api.impossi.build/pricing.json): Request-time model and price discovery.