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Agent Skills

fast-agent supports Agent Skills, and looks for them in either the .fast-agent/skills or .claude/skills folder.

When valid SKILL.md files are found:

  • The Agent is given access to an execute tool for running shell commands, with the working directory set to the skills folder.
  • Skill descriptions from the manifest and path are added to the System Prompt using the {{agentSkills}} expansion. A warning is displayed if this is not present in the System Prompt.
  • The /skills command lists the available skills.

Skill Marketplace

fast-agent can install skills from online registries. By default, two registries are configured:

Installing Skills

Use the /skills add command to browse and install skills from the marketplace:

/skills add

This displays available skills with numbers. Install by name or number:

/skills add 1
/skills add skill-name

Removing Skills

Remove installed skills with /skills remove:

/skills remove skill-name
/skills remove 1

Managing Registries

View the current registry and available registries:

/skills registry

Example output: 

# skills registry

Registry: https://github.com/huggingface/skills

Available registries:
- [1] https://github.com/huggingface/skills
- [2] https://github.com/anthropics/skills

Usage: `/skills registry [number|URL]`

Switch registries by number or provide a custom URL:

/skills registry 2
/skills registry https://github.com/my-org/my-skills

Configuration

Configure skill directories and registries in fastagent.config.yaml:

skills:
  directories:
    - ".fast-agent/skills"
  marketplace_urls:
    - "https://github.com/huggingface/skills"
    - "https://github.com/anthropics/skills"

See the Configuration Reference for details.

Command Line Options

If using fast-agent interactively from the command line, the --skills <directory> switch can be used to specify the directory containing skills..

# Specify a skills folder and a model
fast-agent --skills ~/skill-development/testing/ --model gpt-5-mini.low

# Give fast-agent access to the shell
fast-agent -x

Programmatic Usage

Skills directories can be defined on a per-agent basis:

# Define the agent
@fast.agent(instruction=default_instruction, skills=["~/source/skills"])
async def main():
    # use the --model command line switch or agent arguments to change model
    async with fast.run() as agent:
        await agent.interactive()

This allows each individual agent to use a different set of skills if needed.