# Semantic Kernel Python + Azure OpenAI o3: Unsupported parameter max_tokens, use max_completion_tokens
Invoking Semantic Kernel Python's AzureChatCompletion against an o3-series reasoning model failed with "Unsupported parameter: 'max_tokens' is not supported with this model. Use 'max_completion_tokens' instead." Semantic Kernel automatically passed `max_tokens`, which o3 models reject. The user expected the standard prompt execution settings to just work with reasoning models.
## How to handle it
Configure `max_completion_tokens` instead of `max_tokens`: in SK Python, `OpenAIChatPromptExecutionSettings` (the base class for OpenAI prompt execution settings) has a `max_completion_tokens` attribute, and the child `AzureChatPromptExecutionSettings` adds `extra_body` if needed. Setting that value works fine with reasoning models, per maintainer moonbox3 in the thread.
Source: https://github.com/microsoft/semantic-kernel/issues/12865