Which Agent Should You Build?

Start with the job

Three agent patterns can look like the same chat window. The choice starts with what the agent must accomplish: answer a question from existing content, or do something in another system.

Write down the user, the question or task, and the result they need before choosing a tool. An agent is only useful when that result solves a real problem.

Architecture

Follow the decision tree from the first question. The action requirement is the main dividing line; content location, audience, and conversation control narrow the remaining choice.

Does it need to act?

If the requirement includes writing data, triggering a process, or calling a system, this guide points to Copilot Studio. Plan the action, its permissions, and its owner alongside the conversation.

If the requirement is only to answer, continue to the content and audience questions before choosing the more involved pattern.

Where are the content and the audience?

For answers from one SharePoint site that only need to run there, the tree points to a SharePoint agent owned by the site owner.

For an audience in Microsoft 365 Copilot Chat, where instructions are enough to guide the conversation, the tree points to Agent Builder.

When the requirement needs explicit branching or broader delivery channels, the tree points to Copilot Studio. Environment strategy, solution ownership, governance, and consumption forecasting become part of the design.

Start with the simplest pattern that fits

Use the smallest pattern that meets the requirement, then reassess when the requirement changes. Keep the source content and intended behaviour clear so a move to a more capable pattern has a defined starting point.

The most common wrong answer is building an agent for a use case nobody had. Validate the need before investing in the implementation.