Key insight

The Microsoft 365 Agents SDK is a framework for building full-stack, multi-channel agents — agents that operate across many surfaces inside Microsoft 365 rather than being locked into a single app. When building with the Microsoft 365 Agents Toolkit, developers choose between this SDK for breadth across channels, and the Teams SDK for depth within Teams specifically. Both plug into the same professional development environment, so the choice is about where the agent needs to show up, not about which tooling experience you get.

An agent that only ever appears in one place is only ever half-useful, because people do not spend their whole day in one place either. This article explains the tool built specifically to solve that problem: an agent built once, available everywhere the person already works.

1 · Why one app is never enough

Picture a real employee’s day. They chat with colleagues, read and send email, edit documents, and jump back and forth between all three, often within the same hour. If a helpful agent only shows up in one of those tools, it is useful only during the slice of the day the person happens to be in that particular app. The natural fix is an agent that follows the person across the surfaces they actually use, rather than asking the person to remember which tool holds which assistant.

2 · What the Microsoft 365 Agents SDK is

The Microsoft 365 Agents SDK, a software development kit (a set of code libraries a developer builds on), is a framework designed for building full-stack, multi-channel agents that can operate across Microsoft 365. It is one of the two software development kits developers choose between when building with the Microsoft 365 Agents Toolkit, the professional pro-code environment covered in the previous article.

3 · Full-stack and multi-channel, unpacked

Full-stack means the software development kit covers the complete journey of building an agent, from the underlying logic through to how it presents itself, rather than one narrow slice a developer would otherwise have to stitch together with separate tools themselves. Multi-channel means the same agent logic can appear in several different places — a chat surface, a productivity app, wherever the person happens to be — without being rebuilt from scratch for each one.

Put together, these two properties mean a developer writes an agent’s behaviour once and it can travel with the person across the tools they already use, rather than becoming several disconnected agents that each need separate maintenance.

One agent built once, appearing across several channels A central agent box connects to three channel boxes labelled chat, email, and productivity app, illustrating one agent logic reaching multiple channels. One agent Chat   Email Productivity app Wherever they work
Figure 1. One agent, built once with the Microsoft 365 Agents SDK, can appear across multiple channels rather than needing separate versions for each place a person works.

4 · The choice: Agents SDK vs Teams SDK

Within the Microsoft 365 Agents Toolkit, a developer chooses between two software development kits depending on need. The Microsoft 365 Agents SDK favours breadth: an agent that operates across multiple channels. The Teams SDK favours depth: a tool focused specifically on the Teams experience, for an agent whose entire purpose lives inside that one channel and benefits from leaning fully into everything Teams specifically offers.

The choice is not about which gives a better development experience — both plug into the same professional toolkit, the same local testing playground, and the same deployment pipelines. It is a decision about where the agent needs to show up: everywhere the person works, or deeply inside one specific, important place.

Breadth vs depth, in one line

Choose the Microsoft 365 Agents SDK when your agent must follow the person across several tools. Choose the Teams SDK when your agent’s whole job lives inside Teams and deserves everything that one channel specifically offers.

5 · Glossary — every short-form term, spelled out

SDK (software development kit)
A set of code libraries a developer uses to build on a platform.
Microsoft 365 Agents SDK
A framework for building full-stack, multi-channel agents that can operate across Microsoft 365.
Full-stack
Covering the complete journey of building something, from underlying logic through to presentation, in one framework.
Multi-channel
The same agent logic appearing across several different surfaces or apps without being rebuilt for each one.
Teams SDK
A software development kit focused specifically and deeply on building agent experiences for Microsoft Teams.
Microsoft 365 Agents Toolkit
The pro-code development environment within which a developer chooses between the Microsoft 365 Agents SDK and the Teams SDK.
Key takeaways

An agent locked into one app is only ever half-available, because people move between apps throughout the day.
The Microsoft 365 Agents SDK is a framework for building full-stack, multi-channel agents, an agent built once that can appear across several surfaces.
Full-stack means the whole build journey is covered; multi-channel means the same logic reaches many places without being rebuilt.
Within the Agents Toolkit, developers choose between this SDK for breadth and the Teams SDK for depth within Teams specifically.
Both SDKs plug into the same professional toolkit, testing playground, and deployment pipelines, so the choice is about where the agent needs to show up, not the development experience.

References

  1. Microsoft Learn, Custom engine agents for Microsoft 365 overview — Microsoft 365 Agents SDK and Teams SDK choice within the Agents Toolkit. learn.microsoft.com