# A practical multi-model API, from first call to production

> KeepRouter combines a public model catalog, compatible API surfaces, prepaid usage, scoped keys, request-level metering, and route-specific multimodal endpoints in one managed service.

Start with the client format your application already speaks, then choose a model from the live catalog. Each feature page below explains the contract, operational boundary, and evidence you can inspect before creating a key.

## [Unified LLM API](https://keeprouter.com/features/unified-llm-api.md)

A unified LLM API gives your application one account and authentication layer for multiple model makers. It does not mean every model has the same capability or endpoint; KeepRouter publishes the supported route on every model page.

## [OpenAI-compatible API](https://keeprouter.com/features/openai-compatible-api.md)

An OpenAI-compatible API accepts familiar OpenAI SDK request shapes after you change the base URL, key, and model ID. Compatibility is operation-specific, so KeepRouter lists the supported endpoint on each model page.

## [Anthropic-compatible API](https://keeprouter.com/features/anthropic-compatible-api.md)

KeepRouter exposes an Anthropic-compatible /v1/messages route for supported chat models. Claude Code and the Anthropic SDK can point at the same base URL, while model-specific capabilities still require testing.

## [Model routing](https://keeprouter.com/features/model-routing.md)

KeepRouter routes a request from its public model ID to an eligible configured channel. The public response keeps the requested canonical identity, while route health and availability remain operational concerns rather than hidden marketing claims.

## [Usage-based billing](https://keeprouter.com/features/usage-based-billing.md)

KeepRouter uses prepaid USD credit with no recurring subscription. The catalog publishes the current customer rate for each model, and successful requests record measured usage and the resulting charge.

## [API observability](https://keeprouter.com/features/api-observability.md)

KeepRouter records the operational metadata needed to explain a request—model, route, status, token counts, cost, cache state, and latency—without writing prompt or completion bodies to the request log.

## [Multimodal model APIs](https://keeprouter.com/features/multimodal-models.md)

KeepRouter presents multiple model modalities in one catalog while preserving the endpoint and price unit each operation requires. Unified discovery does not flatten unlike payloads into a misleading universal request.