Agent Harness Construction
Design and optimize AI agent action spaces, tool definitions, and observation formatting for higher completion rates.
- Type
- Skill
- Repository
- affaan-m/ECC
- GitHub stars
- 268k
- License
- MIT
- Repo last updated
- Sep 24, 2026
What Agent Harness Construction is
Agent Harness Construction is a skill published in the affaan-m/ECC repository on GitHub, which has about 268k stars. The repository describes itself as: “The agent harness performance optimization system. Skills, instincts, memory, security, and research-first development for Claude Code, Codex, Opencode, Cursor and beyond.”
A skill is a folder with a SKILL.md file: frontmatter with a name and a description, followed by instructions Claude follows. Claude loads a skill automatically when a task matches its description, and you can also run it directly with a slash and its name.
Skills work in Claude Code and in Claude Cowork, which makes Agent Harness Construction a portable way to give Claude the same method everywhere.
How to install Agent Harness Construction
Claude Code
- Download the agent-harness-construction folder from the repository.
- Save it as ~/.claude/skills/<skill-name>/SKILL.md for all projects, or .claude/skills/<skill-name>/SKILL.md for one project.
- Claude loads it automatically when a task matches; you can also run it with / and its name.
Claude Cowork
- Zip the skill folder so SKILL.md sits at the top level of the folder.
- Open Customize → Skills, click +, then upload the ZIP.
- Start a task that matches the description, or call it by name with /.
New to extending Cowork? Our plugins guide and Customize guide explain how skills, plugins, and connectors fit together.
Inside the source file
We couldn't retrieve the source file for this entry. Browse the repository on GitHub to find it and read the README before installing.
Before you install
- Read the whole file first. Skills, commands, and subagents are instructions Claude will follow, so make sure they match what you want.
- Check which tools, scripts, or MCP servers it uses. Local servers and scripts run with your permissions.
- Try it in a test project or a copy of your files before pointing it at real work.
- Pin the version you tested, and review changes before updating.
- Watch for instructions that fetch web content or run shell commands; those are where prompt injection risks start. See our prompt injection guide.
FAQ
What is Agent Harness Construction?
Agent Harness Construction is a skill for Claude Code and Claude Cowork from the affaan-m/ECC repository on GitHub. Design and optimize AI agent action spaces, tool definitions, and observation formatting for higher completion rates.
How do I install Agent Harness Construction in Claude Code?
Download the agent-harness-construction folder from the repository. Save it as ~/.claude/skills/<skill-name>/SKILL.md for all projects, or .claude/skills/<skill-name>/SKILL.md for one project. Claude loads it automatically when a task matches; you can also run it with / and its name.
Can I use Agent Harness Construction in Claude Cowork?
Zip the skill folder so SKILL.md sits at the top level of the folder. Open Customize → Skills, click +, then upload the ZIP. Start a task that matches the description, or call it by name with /.
Is Agent Harness Construction safe to install?
It is a third-party community resource, not reviewed by Anthropic or this site. Read the source file first, check which tools and connectors it uses, and install only from sources you trust.
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