Microsoft 365 Developer Blog
A developer platform for building collaborative apps for hybrid work
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Bring your own agents into Microsoft 365 Copilot
Custom Engine Agents now generally available—build and integrate your own AI into the flow of work Microsoft 365 Copilot is redefining how people interact with AI—embedding it directly into the flow of work as the intuitive, natural interface for agents: the ‘UI for AI’ As Copilot becomes the interface for AI in the workplace, we’re seeing growing demand from customers who want to extend its capabilities with their own solutions. Many of our customers are looking to create custom agents—or have already built agents that operate outside the Microsoft 365 ecosystem—using fine-tuned models, custom logic, orchest...
Supercharge your EWS migration with AI and GitHub Copilot
We're announcing a new tutorial that helps developers migrate solutions from EWS to Microsoft Graph using AI and GitHub Copilot.
Microsoft 365 Copilot APIs: Unlocking enterprise knowledge for AI with the Retrieval API — Now in Public Preview
Read how the Retrieval API gives developers a secure, compliant and scalable way to integrate enterprise content into their AI workflows.
Dev Proxy v0.29 with refactored architecture, MCP server, and exposed LM prompts
Introducing Dev Proxy v0.29, with a major architectural overhaul, control over language model prompts, and improved diagnostics.
Deprecation of MS-APP-ACTS-AS header in Shifts Management Microsoft Graph APIs
In app-only access scenarios, Shifts Management Graph APIs previously required the MS-APP-ACTS-AS: userId header to indicate the user on whose behalf the application was acting. However, this conflicted with the Microsoft Graph permission model where there is no signed-in user for app-only access scenarios. To align Shifts Graph APIs with this model, the MS-APP-ACTS-AS header has now been deprecated. What Action You Need to Take If you don’t send the header today There is no impact. No changes are necessary. If you send the header today 1. Please remove the header. Example: Old: New: ...
Dev Proxy v0.28 with LLM usage and costs tracking
The latest version of Dev Proxy introduces a new ability to help you understand language models’ usage and costs in your applications, alongside many improvements to mocking, TypeSpec generation, and plugin flexibility.
Build like Microsoft: Developer agents in action
Take a deep dive into Athena, an AI-powered collaborative agent, to learn how it was built and how to create your own version of Athena right within Microsoft Teams.
Office Add-ins announces Copilot agents with add-in actions and more at Build 2025
As part of the expanding capabilities for agents across Microsoft 365, Office Platform announces add-in actions for Copilot agents are available in preview. This blog is an overview of all the new capabilities across the platform: APIs, developer tools, and add-in distribution options—making it simpler to build new or iterate on JavaScript add-ins.
Introducing the Agent Store: Build, publish, and discover agents in Microsoft 365 Copilot
We’re excited to introduce the Agent Store — a centralized, curated marketplace that features agents built by Microsoft, trusted partners, and customers. The Agent Store offers a new, immersive experience within Microsoft 365 Copilot that enables users to browse, install, and try agents tailored to their needs.