What is an API endpoint?
An API endpoint is a specific URL that accepts requests and returns responses from a service. For language model APIs, the endpoint typically accepts a JSON payload containing the model name, messages, and parameters — and returns a JSON response containing the generated text and usage metadata.
OpenAI’s chat endpoint is https://api.openai.com/v1/chat/completions. Anthropic’s is https://api.anthropic.com/v1/messages. Each provider has a different URL, authentication method, and request format.
Why it matters
If you are building an application that needs to work with multiple model providers, the endpoint differences matter. Tools like LiteLLM and OpenRouter exist specifically to normalise these differences — you call one endpoint and it routes to any provider. sourc.dev tracks API compatibility and endpoint structure for every provider entity.