Get reasoning summaries from Azure OpenAI Reasoning Models using the Responses API (.NET)

Reasoning models are awesome for multi-step problems, but in real apps you also want some visibility into how the model got there—without exposing full chain-of-thought. In Azure OpenAI, the right pattern is to request a reasoning summary via the Responses API and log/print it next to the final answer.

On a high level, we’ll:

• Deploy or reuse an Azure OpenAI reasoning model deployment

• Call Azure OpenAI using the v1 base URL (/openai/v1/)

• Request a reasoning summary with a chosen reasoning effort

• Print reasoning summary + final answer in a minimal .NET console app

Prereqs

• Azure OpenAI resource + a deployed reasoning-capable model (e.g. GPT-5 reasoning variants)

• .NET 8+

• Latest OpenAI .NET SDK (OpenAI) that includes ResponsesClient and CreateResponseOptions

1) Create (Or Confirm) Your Reasoning Model Deployment

In Azure AI Foundry:

• Click path: Azure AI Foundry portal → OpenAI → Deployments → + Create deployment

• Pick a reasoning model and give it a deployment name (example: gpt-5-mini)

• Keep that deployment name handy (you’ll pass it to the client)

2) Create a Console App + Install the SDK

3) Call the Responses API and Print the Reasoning Summary

This sample is wired to Azure OpenAI’s v1 endpoint and Responses API.

Change these values:

• AZURE_OPENAI_ENDPOINT (your Azure OpenAI resource endpoint)

• AZURE_OPENAI_API_KEY

• AZURE_OPENAI_DEPLOYMENT (your deployment name, not the base model name)

Why “summary” (not full reasoning): Azure OpenAI’s model behavior is centered on reasoning summaries rather than returning raw reasoning_content.

4) Minimal working example

Expected output (example):

 

Troubleshooting

• 404 Not Found: your deployment name is wrong, or the deployment/region doesn’t support Responses API. Start by verifying deployment name in the portal.

• 400 Bad Request: most often you’re not using the v1 base URL (.../openai/v1/).

• No reasoning summary returned: your deployment might not be a reasoning model, or the model chose not to emit a summary. Confirm model capability and try ReasoningSummaryVerbosity = Concise/Detailed if available in your SDK/version.

• Compile errors for Responses types: upgrade the OpenAI .NET SDK class names have changed (e.g., CreateResponseOptions).

• 401 Unauthorized: API key doesn’t match the resource or is missing.

Notes

• Reasoning summaries are the “sweet spot”: better debugging/telemetry without leaking full internal chain-of-thought. Azure’s docs explicitly separate Azure OpenAI from providers that emit reasoning_content.

• If you’re building Copilot/agent experiences, this summary is exactly what you’d stash in app logs or a trace store for support cases. Keep the final answer user-facing.

Wrapping up

If you want a clean, production-friendly way to understand what a reasoning model did without capturing the full chain-of-thought, use the Responses API and print/log the reasoning summary next to the final answer. 

Hope this helps!