Two Microsoft product names, real functional overlap, and a question that comes up on every team getting started on Azure: which one do I use?
Azure OpenAI Service is a model API; Azure AI Foundry is an AI application platform. More specifically: Azure OpenAI Service is a managed service focused exclusively on giving access to OpenAI's models (the GPT-5 series, GPT-4o, GPT-4.1, embeddings, multimodal models), while Azure AI Foundry is a broader, unified platform for building, customizing, deploying, and managing AI applications and agents.
Azure OpenAI Service gives you API access to foundation models; Azure AI Foundry gives you a complete "production plant" for building AI products on top of those models. Azure AI Foundry includes the model API's capabilities -- but not vice versa: you can't access Foundry's agent, orchestration, or observability features with Azure OpenAI Service alone.
Microsoft Foundry is a consolidation of Azure OpenAI plus Azure AI Studio plus Azure AI Services into a single resource that exposes three FQDNs and adds non-OpenAI models, agents, and observability -- it's, literally, a merger of products that used to live separately, unified under one management plane.
It's worth clarifying: Azure OpenAI Service is not deprecated. The SKU can still be created, it still works, and it still receives new GPT models. There's no announced end-of-life date forcing an immediate migration.
If you're building agents, need non-OpenAI models on a single Azure bill, or already have an Assistants API deployment, migrating to Foundry is the direct recommendation. If your use case is simple -- calling a GPT model via API with no need for agents or multi-provider access -- Azure OpenAI Service remains a completely valid, simpler-to-operate option, with no need to adopt Foundry's broader surface.
Carlos Montiel is an enterprise AI solutions architect. He implements LLMs, Agents, RAG, and orchestrators for companies across Guatemala and Latin America. Reach out for a consultation.
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