# Singular > OpenAI Chat Completions-compatible model routing with a live multi-provider catalog, prepaid billing, limited BYOK attachment, and deployment-gated x402/MPP per-call payments. Canonical human docs: https://singular.impossibuild.ai/docs Canonical OpenAI SDK base URL: https://api.impossi.build/v1 Updated: 2026-08-10 Use OpenAI Chat Completions for the current public API. Supporting that endpoint does not imply OpenAI Responses or universal native Anthropic Messages compatibility. Fetch live model IDs and rates before choosing a model. ## 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. ## Machine-readable sources - [Live retail pricing](https://api.impossi.build/pricing.json): Current public model IDs, names, positive retail rates, and context values. - [Full documentation](https://singular.impossibuild.ai/llms-full.txt): Complete Markdown documentation corpus. - [Technical documentation index](https://singular.impossibuild.ai/docs/llms.txt): API-oriented index. ## Optional - [Model browser](https://singular.impossibuild.ai/models): Human-readable searchable catalog. - [Pricing](https://singular.impossibuild.ai/pricing): Human-readable billing and rate overview. - [Web application](https://singular.impossibuild.ai): Consumer chat workspace.