015 - Agent Builder or Copilot Studio? Building agents in Microsoft 365

Agent Builder or Copilot Studio: where should you actually build an agent in Microsoft 365, and do you even need an agent, or was it a flow all along?

In episode fifteen of 365 Explained, Ben and Zach finally deliver the agents episode we promised back in the Power Automate one. Ben opens by admitting his agent count is padded with sub-agents, then walks through building an agent in Agent Builder and what's inside Copilot Studio. Microsoft renamed one of the harnesses the night before we recorded, so this is accurate as of 29 October 2026 (and quite possibly not by the time you hear it).

In this episode, we explore:

◆ Agent or flow? If the job is "find this, pull that out, do the same thing every time", it's a flow. An agent earns its place when there's ambiguity to work through

◆ Skills: the instructions you'd otherwise paste into every chat. They're just Markdown files, so they travel between Copilot, Claude and ChatGPT, and they're far less of a sprawl risk than agents

◆ Agent Builder end to end: describe the agent, refine its instructions, add skills and knowledge, preview it and share it

◆ Why the agent you share may not answer your colleague the way it answers you, because knowledge runs on their permissions, not yours

◆ Copying an agent to Copilot Studio makes a copy, not a migration, and the harness changes underneath it, so test it again

◆ When to move up to Studio: external tools and MCP servers, flows, evaluations, or picking the model yourself

◆ What a harness actually is, and why it matters more than which model you choose

◆ Licensing: Agent Builder sits inside the $30 Microsoft 365 Copilot licence, but the new Microsoft Copilot harness in Studio runs entirely on usage-based billing, licence or not

◆ Governance through Agent 365, and why you still need a human process for who owns an agent and why it exists

◆ The classic harness in Copilot Studio: model picker, MCP tools, sub-agents and evaluations (where answering "I don't know" counted as a fail, which was rather the point)

◆ The new harness: newer models, skills and memory, so an agent gets better for you over time

◆ Agent flows and workflows, where a flow hands the fuzzy middle step to an agent

◆ How to build anything when the platform changes overnight

Whether you've been asked to "build an agent" and suspect it's really a flow, or you've been avoiding Copilot Studio because it looks complicated, this one's for you. Ben's advice: find a stupid problem and build an agent that solves it.

What's the daftest problem you've solved with an agent? Let us know.

Follow the show for a new episode every month (ish). The video version, with the screen walkthroughs, is on YouTube: https://youtu.be/2KjSvjmMJ5g