Add custom skills to your declarative agent in Agent Builder (preview)

A custom skill is a modular, reusable component that you add to a declarative agent to help it perform a specific packaged task. A skill is a directory that contains a required SKILL.md file with instructions, plus optional resource files and scripts. This article describes how to add a custom skill to an agent built in Agent Builder, either by describing the skill in natural language or by uploading a skill package.

Skills in Agent Builder are in preview and are available only to organizations enrolled in the Microsoft Frontier Program.

To learn what custom skills are, why to use them, and the full support matrix, supported file types, sandbox behavior, and governance, see Custom skills in declarative agents (preview).

Important

Custom skills in declarative agents are in preview for organizations that are part of the Microsoft Frontier Preview. For more information, see Explore AI Early Access in Microsoft 365.

Custom skills aren't available in tenants that use Microsoft Purview Information Barriers (IB). This restriction applies to both admin-deployed and user-created declarative agents.

Support for independent software vendors (ISVs) to publish declarative agents with custom skills through Partner Center isn't available yet and is coming soon. ISVs shouldn't submit declarative agent packages that include custom skills to Partner Center.

Prerequisites

• A qualifying Microsoft 365 Copilot license, or access through pay-as-you-go. For details, see Agent capabilities and licensing models.
• Your organization must be enrolled in the Microsoft Frontier Program.

Note

In Agent Builder, you can add up to eight skills per agent, and each skill package is a compressed .zip file of up to 50 MB. For the full support matrix and limits, see Custom skills in declarative agents (preview).

Create a skill from a description

You can ask Agent Builder to create a reusable skill from a natural-language description.

1. In Copilot chat, select Agents & Skills, and then select New agent.

2. Select the Message Agent Builder text box and ask Agent Builder to create a reusable workflow.

   Create an agent that helps my team write release notes. Add a reusable skill that always follows the same steps:
   
   1. Takes a list of merged changes (a pasted list or an uploaded  .csv  of PR titles).
   2. Groups them into Features, Fixes, and Other.
   3. Runs a script to format them into a clean Markdown changelog with a version heading and today's date.
   
   Package this as a skill with clear instructions and the formatting script so the output looks the same every time.
   

   

3. On the Configure tab, confirm that a skill was created.

   

4. Select the skill to review its details.

   

If the skill isn't added, you can explicitly add skills by uploading a skill package.

Upload a skill package

To add a skill package, first create the package, and then upload it in Agent Builder.

Create your skill package

Before you add a skill in Agent Builder, package the skill as a .zip file that contains:

• A required SKILL.md file.
• A skill name and description in the SKILL.md YAML front matter.
• Optional supported resource files.
• Optional supported scripts and supporting folders.
• Skill instructions under 20,000 characters.

Your package resembles the following directory structure:

my-skill.zip
|-- SKILL.md              # required
|-- <resource files>      # optional
`-- <scripts or folders>  # optional

For the supported file and script types, see Supported file and script types.

Important

Upload the complete .zip package. Don't upload SKILL.md by itself.

Upload your skill package

1. Open or create a declarative agent in Agent Builder.

2. On the Configure tab, expand Skills, and then select Add.

   

3. Upload the complete .zip skill package.

4. Review the skill name, description, instructions, and included files.

5. On the Try it tab, try a prompt that should use the skill.

Related content

• Custom skills in declarative agents (preview)