What is an application programming interface compatibility layer?
Definition
An application programming interface compatibility layer maps requests, responses and errors from one protocol to another. For model APIs it may convert message roles, reasoning blocks, tool definitions, tool results and token-usage fields while preserving the client's expected workflow.
Reliable compatibility requires semantic translation, not only renaming fields. Providers can interpret tools, streaming, stop conditions and context differently, so unsupported features must fail clearly instead of appearing to work while changing behavior.
Acronyms and aliases
API compatibility layer acronymprotocol compatibility layer synonym
Related terms
Frequently asked questions
What does an AI API compatibility layer translate?
It can translate message formats, reasoning content, tool calls, streaming events, errors and token accounting between client and provider conventions.
Can every provider feature be translated?
No. Some models or APIs lack equivalent capabilities, so the layer must document limits, emulate carefully or reject unsupported requests.
