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What Are Agent Skills? The Open Standard Behind Claude Code

Skilllm Team8 min read
Illustration showing code flowing from a central AI core into modular skill blocks

In the rapidly expanding universe of AI, a new problem has surfaced: "context limits." How do you teach an AI to perform a highly specific, complex task without overwhelming its memory window or re-prompting it endlessly?

The answer lies in Agent Skills—a standardized way to package expertise for AI. While this technology is now an open industry standard, its origins tell a fascinating story about the future of automated coding and AI agency.

The Origin: Built for Claude Code

Before "Agent Skills" became a buzzword for developers, the technology had a specific purpose inside Anthropic.

As Anthropic's engineering team worked on Claude Code—their advanced agent designed to interact with real-world computing environments and filesystems—they hit a wall. To make Claude Code truly effective at complex coding tasks, it needed more than just a large language model; it needed procedural knowledge. It needed to know exactly how to navigate specific codebases, run tests, or format documentation.

They couldn't just "hard code" these abilities into the model itself. They needed a flexible system where abilities could be swapped in and out depending on the task.

The solution was a modular folder structure containing instructions and scripts. It worked so well for equipping Claude Code with domain-specific expertise that Anthropic realized something crucial: this shouldn't remain a proprietary secret.

Going Open Source: A Standard for Everyone

In late 2025, Anthropic made a strategic move. Recognizing that the AI industry needs a common language for "teaching" agents, they released Agent Skills as an open source standard (now hosted at AgentSkills.io).

This shift is significant for the SEO of your AI workflow because it means portability.

  1. Originally: A way for Claude Code to handle files.
  2. Now: A universal format that developers can use to build skills for any compatible agent, not just Claude.

By open-sourcing the format, the community can now build a shared library of skills. A skill written to help an agent "Analyze Financial PDFs" can theoretically be shared and used across different platforms without rewriting the core instructions.

What Are Agent Skills Technically?

If you look under the hood, an Agent Skill is surprisingly simple. It is designed to be human-readable and machine-executable.

A skill is simply a directory (folder) that contains a primary file: SKILL.md.

  1. The Header (Metadata): Contains the name and description. This is what the agent scans to decide if it needs the skill.
  2. The Body (Instructions): Markdown text that tells the agent how to think and what steps to take.
  3. The Tools (Scripts): The folder can also hold Python or Bash scripts that the agent can execute to ensure deterministic results.

The Power of "Progressive Disclosure"

The reason Agent Skills are so SEO-friendly for your agent's "brain" is a technique called Progressive Disclosure.

Instead of reading the entire manual at once, the agent only reads the skill's Description first. Only when it decides, "Hey, I need to fix a database error," does it load the full SKILL.md associated with database management. This keeps the agent lightweight, fast, and cost-effective.

Why You Should Adopt the Agent Skills Standard

If you are building AI agents or using tools like Claude Code, adopting this standard offers three main advantages:

  1. Structure: It forces you to organize your prompt engineering into clean, manageable files.
  2. Control: You can bundle executable code with your instructions, ensuring the agent doesn't hallucinate when performing math or data logic.
  3. Future-Proofing: Since it is now an open standard supported by major players, your skills won't become obsolete if you switch platforms.

Conclusion

What started as a utility to power Claude Code has evolved into a foundational block for the future of AI. Agent Skills are no longer just about Anthropic; they are about creating a shared, open ecosystem where AI agents can learn, adapt, and help us work smarter.

Want to build your first skill? Visit the open repository at AgentSkills.io.