# One managed account for a changing model stack

> 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.

_Last reviewed 2026-08-15 · [Editorial review](https://keeprouter.com/editorial-policy#editorial-team)_

## What is unified

Your KeepRouter key authenticates requests to the models exposed in the production catalog. Compatible chat models can accept OpenAI-style Chat Completions or Anthropic-style Messages requests. Image generation, embeddings, speech, transcription, and other specialized modalities use the route shown on their model page.

That boundary matters. A trustworthy unified API normalizes the parts that can be normalized—account, key, catalog, billing, and compatible request shapes—without pretending that an image model and a chat model share one universal payload.

## The working contract

- **Discover:** use the [model catalog](/models) to verify ID, maker, modality, endpoint, and current customer price.
- **Authenticate:** create one `sk-kr-` key, optionally scoped to a model allowlist and spending limit.
- **Call:** keep the client format supported by the selected model and point its base URL at KeepRouter.
- **Measure:** inspect request status, token usage, cost, cache state, and latency in the console.
- **Change:** switch the model ID only after checking that the replacement supports the same route and features.

## Where this reduces work

The account and billing relationship stays stable while a team evaluates different model makers. A prototype can begin with the published free model, record a representative request, then compare paid candidates using the same usage view. Production code keeps a bounded set of client integrations instead of adding a new billing account and secret for every experiment.

## Where your application still owns decisions

Model behavior, context limits, tool semantics, safety settings, and output quality are not interchangeable. KeepRouter exposes routing and protocol compatibility; your tests decide whether a model is suitable. Store model choice in configuration, run a reproducible evaluation, cap output tokens, and handle provider-shaped errors even when the client format is stable.

## Start with evidence

Run the [quickstart](/docs/quickstart) against `free`, then open the request in Usage. Once authentication, streaming, and error handling are proven, choose a paid model from the live catalog and set a key-level model allowlist before adding credit.

## Frequently asked questions

### Does one API mean one endpoint for every model?

No. Compatible chat models share supported client formats, while specialized modalities use their documented route-specific endpoints.

### Do I need a separate provider account?

Not for models purchased through KeepRouter's managed catalog. You fund prepaid KeepRouter credit and use a KeepRouter key.

### Can I restrict a key to specific models?

Yes. Self-serve keys support a model allowlist and optional spend controls so an application does not automatically inherit the whole catalog.

### Where do I check current model availability?

Use the live model catalog and each model detail page. Static marketing pages do not preserve a model-count or price snapshot.

## Sources reviewed

1. [KeepRouter OpenAPI](https://keeprouter.com/api/openapi.json)
2. [KeepRouter live model catalog](https://keeprouter.com/models)

## Related guides

- [Model routing](https://keeprouter.com/features/model-routing.md)
- [Usage-based billing](https://keeprouter.com/features/usage-based-billing.md)
- [How do I use one API for multiple LLMs?](https://keeprouter.com/answers/how-to-use-one-api-for-multiple-llms.md)
- [quickstart](https://keeprouter.com/docs/quickstart.md)

## Prove the path with a free request

Create a free-model-scoped key and inspect the measured request before funding a paid model.

[Create a free key](https://keeprouter.com/login?returnTo=%2Fconsole%2Fkeys%3Fmodel%3Dfree) · [Live models and pricing](https://keeprouter.com/models.md)