Agent Skills: Reusable Instruction Sets Your AI Agents Load on Demand

If you've built more than one AI agent, you've probably copy-pasted the same instructions into multiple system prompts. "Keep responses concise." "Cite your sources." "Format as bullet points."

Skills fix this. A skill is a standalone SKILL.md file — published once, usable by any agent, loaded on demand.

What's a Skill?

A skill follows the AgentSkills.io specification:

---
name: concise-answers
description: Keep responses short, cite tools used, prefer bullet points
---

## Instructions

Keep every response under 150 words. Always name the tool you used.
Prefer bullet points over prose.

That's it. YAML frontmatter for metadata, markdown body for instructions.

Why Not Just Stuff It in the System Prompt?

Token cost. A 500-word skill in the system prompt costs tokens on every single turn — even when the user's question has nothing to do with that skill.

The AgentSkills plugin uses progressive disclosure: only a one-line summary appears in the system prompt. The agent calls a skills tool to load the full instructions only when it needs them.

Using Skills in Your Agent

from strands import Agent
from strands.models import BedrockModel
from strands.vended_plugins.skills import AgentSkills

agent = Agent(
    model=BedrockModel(model_id="us.amazon.nova-pro-v1:0"),
    plugins=[AgentSkills(skills=[
        "https://api.universalapi.co/skills/s/snowtimber/concise-answers/SKILL.md",
    ])],
)

One line per skill. The plugin handles fetching, parsing, injection, and activation.

Creating Your Own

Via the API

curl -X POST https://api.universalapi.co/skills/create \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "skillMd": "---\nname: my-skill\ndescription: ...\n---\n\n## Instructions\n...",
    "visibility": "public"
  }'

Via the UI

Navigate to universalapi.co/skills → Create Skill → paste your SKILL.md → done.

Starter Skills

Three skills are available today:

Skill	Best For	Raw URL
concise-answers	Any agent that should be brief	SKILL.md
uapi-agent-authoring	Agents that build other agents	SKILL.md
mcp-tool-design	Agents that design MCP server tools	SKILL.md

Discoverable & Searchable

Skills are first-class resources in the Universal API catalog. Search for them:

GET /search?q=concise&type=skill

Or via the MCP server:

search_resources(query="formatting", type="skill")

Star your favorites, browse by author, and the AI classification pipeline automatically tags each skill with domain, capabilities, and risk flags.

What's Next

This is the foundation. On the roadmap: skill bundles with scripts/ and references/ directories, version pinning via ?v=N on raw URLs, and paid skill subscriptions for authors.

Try it now: universalapi.co/skills | Docs | API Reference