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API plugins for Microsoft 365 Copilot

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API plugins enable declarative agents in Microsoft 365 Copilot to interact with REST APIs that have an OpenAPI description. With an API plugin, users can ask a declarative agent to not only query a REST API for information, but to create, update, and delete data and objects. Anything the REST API can do is accessible via natural language prompts.

Important

API plugins are only supported as actions within declarative agents. They are not enabled in Microsoft 365 Copilot.

An API plugin provides an OpenAPI description document and a plugin manifest that Copilot uses to learn the capabilities of the API. Copilot can then decide when an installed and enabled plugin's API is suited to answer any given prompt. To learn more about the manifest file that an API plugin requires, see API plugin manifest schema for Microsoft 365 Copilot.

For example, consider a budgets API that allows for querying and creating budgets, charging expenses, or adding funds to existing budgets. The prompt "How much is left in the Contoso travel budget" could trigger a budget plugin, making the following API call.

GET /budgets?name=contoso%20travel

Copilot uses the response from the API call to generate its response: "The Contoso travel budget currently has $5,000 in available funds. If you need to allocate funds to specific categories or track expenses, I can assist you with that as well. Just let me know how I can help!"

The prompt "Charge $500 to the Contoso travel budget for Megan's airline ticket" could be translated to the following API call.

POST /budgets/charge
Content-Type: application/json

{
  "budgetName": "Contoso travel",
  "amount": 500,
  "description": "Megan's airline ticket"
}

Copilot responds to the user, using the information returned: "The charge of $500 for Megan's airline ticket has been successfully processed. The Contoso travel budget now has $4,500 remaining in available funds. If you need to make any more transactions or require further assistance with your budget, please let me know!"

Confirming actions

Copilot asks the user before sending any data to an API plugin.

A screenshot of a plugin confirmation dialog.

By default, APIs that only retrieve data give the user an "Always allow" option, while APIs that modify data don't. Plugin developers can override these defaults. For details, see Confirmation prompts for API plugins for Microsoft 365 Copilot.

Customizing response presentation

Copilot generates conversational responses using data from API responses. Plugins can customize these responses by providing Adaptive Card templates to display data in a structured way.

A screenshot of an Adaptive Card response from an API plugin

Generating API plugin packages

There are two tools developers can use to generate API plugin packages.

  • The Teams Toolkit in Visual Studio or Visual Studio Code can create plugin packages based on an existing OpenAPI description. If you don't have an existing API, Teams Toolkit also has starter projects with an example API and corresponding plugin package.
  • Kiota is a command line tool and a Visual Studio Code extension that can generate plugin packages based on an existing OpenAPI description.

Limitations

URLs in API responses are redacted

To protect the user's privacy, Copilot redacts any URLs contained in API responses. The sole exception to this behavior is any URL in a property specified by the url property in the Response semantics properties object.

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