Spettro
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Agent Skills

Spettro implements the Agent Skills standard so you can install reusable capability packs once and have every Spettro agent (planning, coding, exploring, reviewing, etc.) pick them up automatically. Skills are also compatible with Claude Code and other clients that use the same SKILL.md format.

What is a skill?

A skill is a directory containing a SKILL.md file with YAML frontmatter and Markdown instructions, plus optional bundled scripts/, references/, and assets/ subdirectories:

pdf-processing/
├── SKILL.md
├── scripts/
│   └── extract.py
├── references/
│   └── REFERENCE.md
└── assets/
    └── template.docx

Minimum frontmatter:

---
name: pdf-processing
description: Extract PDF text, fill PDF forms, merge PDFs. Use when handling PDF documents.
---

Optional fields are license, compatibility, metadata (key/value map), and allowed-tools.

Discovery roots

Spettro scans the following directories at every agent run, in priority order (the first occurrence of a name wins, project-scope overrides user-scope):

Scope Path
project <cwd>/.spettro/skills/
project <cwd>/.agents/skills/
project <cwd>/.claude/skills/
project <cwd>/.openai/skills/
user ~/.spettro/skills/
user ~/.agents/skills/
user ~/.claude/skills/
user ~/.openai/skills/

Skills already installed for Claude Code under ~/.claude/skills/ or shared ~/.agents/skills/ are discovered automatically without any extra setup. You can see the live list with /skill where.

Slash commands

Command Description
/skill list (or /skills) Show installed skills + scope/source.
/skill install <source> [--project] [--force] [--as=<name>] [--path=<sub>] Install from a local directory, https git URL, or owner/repo.
/skill info <name> Show metadata, resources, and a body excerpt.
/skill enable <name> / disable <name> Toggle a skill without uninstalling.
/skill uninstall <name> [--project] Remove an installed skill.
/skill where List every discovery root and whether it exists.
/skill reload Re-scan skill directories.

Install sources

/skill install ./local-skill-folder
/skill install ~/Downloads/my-skill
/skill install https://github.com/anthropics/skills.git --path=skills/pdf
/skill install anthropics/skills --path=skills/pdf

The default destination is ~/.spettro/skills/<name>. Use --project to install into <cwd>/.spettro/skills/<name> instead so the skill ships with the repository.

How agents use skills

At every run, Spettro injects an <available_skills> block into the system prompt with name, description, location, and bundled resources for each enabled skill. Agents have two activation paths:

  1. Dedicated tool (preferred): the skill-read builtin returns the skill body wrapped in <skill_content name="..."> tags so it is identifiable during compaction. The model invokes it with the native skill-read tool with {"name":"<skill>"}.
  2. File read: the model can also read SKILL.md directly via the standard file-read tool, using the absolute location from the catalog.

Bundled scripts and references are listed but not eagerly read; the model loads them on demand when the skill instructions reference them.

Authoring a skill

mkdir -p ~/.spettro/skills/my-skill
cat > ~/.spettro/skills/my-skill/SKILL.md <<'EOF'
---
name: my-skill
description: Short summary plus when to use it.
---

# My Skill

1. Step one
2. Step two
EOF
/skill list

Spettro applies lenient validation: it warns when name does not match the parent directory or exceeds 64 characters, but still loads the skill so you can iterate quickly.