Question about missing service_tier support in Azure OpenAI OpenAPI specifications

[istrate23]

Relevant references:

Azure Priority Processing documentation

• https://learn.microsoft.com/en-us/azure/foundry/openai/concepts/priority-processing?tabs=global-standard

Legacy inference OpenAPI spec

• https://github.com/Azure/azure-rest-api-specs/blob/main/specification/cognitiveservices/data-plane/AzureOpenAI/inference/preview/2025-04-01-preview/inference.json

Azure OpenAI v1 generated spec

• https://github.com/Azure/azure-rest-api-specs/blob/main/specification/ai/data-plane/OpenAI.v1/azure-v1-v1-generated.json

Azure OpenAI v1 preview generated spec

• https://github.com/Azure/azure-rest-api-specs/blob/main/specification/ai/data-plane/OpenAI.v1/azure-v1-preview-generated.json

Example of strict request body schema (additionalProperties: false)

• https://github.com/Azure/azure-rest-api-specs/blob/main/specification/ai/data-plane/OpenAI.v1/azure-v1-preview-generated.json#L10116

We are integrating Azure OpenAI using both:

legacy inference spec:

• inference/preview/2025-04-01-preview/inference.json

new v1 specs:

• azure-v1-v1-generated.json

and

• azure-v1-preview-generated.json

According to the Azure Priority Processing documentation, service_tier should be supported for Chat Completions and Responses APIs, for example:

   {
     "model": "gpt-4.1",
     "input": "This is a test",
     "service_tier": "priority"
    }

However:

service_tier is not present in:

• inference.json
• azure-v1-v1-generated.json
• azure-v1-preview-generated.json

The v1 preview schema uses:

• "additionalProperties": false

on request bodies, which makes generated SDKs reject unknown properties such as service_tier.

Questions:

Is service_tier officially supported for:

• /openai/v1/chat/completions

• /openai/v1/responses

• legacy /openai/deployments/{deployment}/chat/completions

Is service_tier planned only for v1 endpoints, or should it also work with the legacy inference API surface?
( OpenAI Spec - https://raw.githubusercontent.com/openai/openai-openapi/refs/heads/master/openapi.yaml include ServiceTier)