Skills are reusable prompt templates that give agents structured instructions for common tasks — code review, committing, test writing, refactoring, and more. They are discovered automatically from convention directories, listed in the agent’s system prompt, and can be invoked either by the user (with /skill-name syntax) or by the agent itself (via the use_skill tool).
Fabro implements the open Agent Skills format. Each skill is a directory containing a SKILL.md file with YAML frontmatter and Markdown instructions. See the Agent Skills specification for the full file format, and What are skills? for an introduction.
Discovery
Fabro discovers skills from three convention directories, searched in order:
| Directory | Scope |
|---|
~/.fabro/skills/ | Global — applies to all projects |
{git_root}/.fabro/skills/ | Project — checked into the repo |
{git_root}/skills/ | Project (alternate location) |
*/SKILL.md files (one level of nesting).
When the same skill name appears in multiple directories, later directories override earlier ones. This means project-level skills take precedence over global skills, letting you customize behavior per-repo.
You can override the default directories by setting skill_dirs in the session configuration. When set, only the specified directories are searched.
Invocation
Skills can be invoked in two ways.
Users can reference a skill with a / prefix in their input:
/commit fix the off-by-one error in pagination
/commit token, finds the matching skill, and expands the input by replacing the skill reference with the full template. The remaining text (fix the off-by-one error in pagination) is substituted into the {{user_input}} placeholder.
Rules for slash syntax:
- The
/ must be preceded by whitespace or be at the start of the input
- The skill name must be followed by whitespace or end of input
- Only one skill reference per input is allowed
- File paths like
/usr/bin/bash are not matched (the character after / must be a lowercase letter, and the name cannot contain /)
When skills are available, Fabro adds a use_skill tool to the agent’s toolset and lists the available skills in the system prompt:
# Available Skills
When the user's request matches a skill below, call the `use_skill` tool
to load its instructions, then follow them.
- `commit`: Create a git commit following best practices
- `review`: Review code changes for issues and improvements
use_skill with a skill name to load the template, then follow the instructions:
| Parameter | Type | Required | Description |
|---|
skill_name | string | yes | Name of the skill to load (without the / prefix) |
Lifecycle
- Discovery — On session startup, Fabro scans the skill directories and parses all valid
SKILL.md files
- Registration — If any skills are found, the
use_skill tool is registered and the skill list is added to the system prompt
- Expansion — When user input contains a
/skill-name reference, Fabro expands it before sending to the LLM
- Tool use — The agent can also call
use_skill at any time to load a skill’s template mid-conversation
