Package an agent skill

Skills are portable instruction packages following the Agent Skills open spec. They use progressive disclosure: the agent sees only names and descriptions until it activates a skill, at which point the full instructions load.

This guide creates a skill in the session workspace. To share a skill across agents organization-wide, see Publish a skill to the registry.

SKILL.md format

Every skill is a directory containing a SKILL.md with YAML front matter:

---
name: csv-analyzer
description: Analyze CSV files and generate summary reports.
metadata:
  category: data-processing
  version: "1.0"
---

# CSV Analyzer

## When to Use

Activate this skill when a user provides a CSV file and wants summary statistics.

## Instructions

1. Read the CSV file using the `read_file` tool
2. Run `scripts/analyze.py` via `bash`
3. Present findings to the user

Required front-matter fields:

Field	Constraint
name	1–64 chars, lowercase alphanumeric + hyphens
description	1–1024 chars, describes when to activate

Optional fields: metadata, license, compatibility.

Bundle scripts and references

Skills can include arbitrary files. The agent accesses them via the session filesystem after activation:

/.agents/skills/csv-analyzer/
├── SKILL.md
├── scripts/
│   └── analyze.py
└── references/
    └── REFERENCE.md

After activation, bundled files mount at /skills/csv-analyzer/ in the session VFS and the agent reads them with the existing read_file / list_files tools.

Enable the skills capability

Add the built-in skills capability to the agent so it can discover and activate skills from the workspace:

curl -X POST http://localhost:9300/api/v1/agents \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Data Analyst",
    "capabilities": [
      { "ref": "skills" },
      { "ref": "session_file_system" }
    ]
  }'

skills depends on session_file_system; the platform pulls it in automatically.

How activation looks to the agent

With the capability enabled, the system prompt includes an <available_skills> block (~100 tokens per skill):

<available_skills>
  <skill>
    <name>csv-analyzer</name>
    <description>Analyze CSV files and generate summary reports.</description>
  </skill>
</available_skills>

When the user’s task matches, the agent calls activate_skill:

{ "name": "activate_skill", "arguments": { "name": "csv-analyzer" } }

The tool returns the full SKILL.md instructions wrapped in <skill> tags. The agent now has the detailed instructions in context and can run the bundled scripts.

Test the skill

1. Start a session with an agent that has the skills capability enabled.
2. Write the skill files to /.agents/skills/<name>/ in the session.
3. Send a message that matches the skill’s “When to Use” criteria.
4. Watch the event stream for an activate_skill tool call.

See also

• Agent Skills feature
• Skills Registry, share skills across the organization.
• Publish a skill to the registry