Agent Skills
Agent Skills are reusable capability packages for AI agents. A skill is usually a folder with a `SKILL.md` file, metadata, task instructions, and optional scripts, references, templates, or assets that the agent loads when the user asks for a matching workflow.
Skills turn repeated agent work from copy-pasted prompts into reusable, inspectable, and version-controlled capability bundles. They matter for coding agents because they can carry workflow rules, commands, project procedures, quality gates, and examples across Claude Code, GitHub Copilot, Codex, Cursor, Gemini CLI, and other compatible hosts.
Anthropic documents Agent Skills as modular capabilities that package instructions, metadata, and optional resources for Claude, with progressive loading and security caveats. The agentskills specification frames skills as an open format based on `SKILL.md`. Microsoft documents Agent Skills as an open standard for Copilot in VS Code, and GitHub documents `gh skill` commands for installation, version pinning, provenance, and supply-chain controls. Hacker News discussion shows demand around practical skills, how people misuse them, and how they differ from prompts, tools, and MCP servers.
- Use skills for reusable agent workflows, not one-off reminders.
- Prefer a `SKILL.md` plus scripts or references when the workflow needs repeatability.
- Keep prompts, tools, MCP servers, and skills conceptually separate when comparing agent systems.
- Audit third-party skills before loading them into sensitive workspaces.
The common shape is deliberately simple: a directory, a `SKILL.md` file with metadata and instructions, and optional supporting files. Those supporting files can be scripts for deterministic work, references for domain facts, examples for style, or templates for repeatable output.
- Discovery metadata tells the agent when the skill may be relevant.
- The main instructions explain the workflow or domain behavior.
- Optional scripts and resources let the agent use repeatable code or reference material without pasting everything into the prompt.
A prompt is usually a conversation-level instruction. A tool is an executable interface the agent calls. A skill sits between them: it teaches the agent a workflow and can point to tools, scripts, references, and templates. That makes skills useful for procedures such as testing, reviewing, document generation, deployment checklists, and domain-specific analysis.
Skills are useful because the agent does not have to load every instruction at startup. It can first see lightweight metadata, then read the full instructions only when a task matches, and finally load referenced files or run scripts only when needed. This keeps context smaller while still making deeper procedures available.
A skill can change how an agent reasons, what commands it runs, and what files or external content it reads. Treat third-party skills like software: inspect the instructions, check bundled scripts, pin versions when possible, and avoid loading unknown skills into sensitive projects without review.
Claude Code is one of the agent hosts where custom skills are used for coding workflows.
A concrete web-agent tool that can be discussed alongside skills, MCP, and browser-control harnesses.
Local MCP connector that shows how project instructions, skills, files, shell access, and worktrees combine in a harness.
Coding harness example where skills are part of the user-facing workflow surface.
The runtime and control layer that discovers, scopes, and executes skills.
The review surface for skill provenance, scripts, permissions, and hidden instructions.
Trace evidence helps verify whether a skill changed an agent run as intended.
Skills package repeatable loops so agents do not recreate the same process from scratch.
Source confidence
Anthropic
Anthropic Engineering
Agent Skills
Microsoft Docs
GitHub Changelog
Anson Biggs
Agent Skills FAQ
Page-level questions for Agent Skills.
Are Agent Skills just prompts?+
No. A prompt is usually a single instruction in a conversation. An Agent Skill is a reusable package with metadata, task instructions, and optional scripts, references, examples, or templates that an agent can load only when a matching task appears.
How are Agent Skills different from MCP tools?+
Agent Skills teach an agent how to perform a workflow. MCP tools expose callable capabilities or external systems. A skill may tell an agent when and how to use an MCP tool, but the skill itself is not the tool server.
Why do Agent Skills need security review?+
Skills can influence planning, tool choice, file access, scripts, and external-source handling. Unknown skills can hide unsafe instructions or commands, so teams should inspect bundled files, pin trusted versions, and avoid loading unreviewed skills into sensitive projects.
When should I create an Agent Skill?+
Create a skill when a workflow is repeated, teachable, and benefits from reusable instructions, scripts, references, or templates. Do not create a skill for a one-off note or a vague preference that belongs in normal project documentation.