AgentToolDrop

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Agent Skills (Addy Osmani)

Adds engineering workflow skills for specs, tests, review and shipping to your coding agent

Install all skills with the skills CLI

npx skills add addyosmani/agent-skills

Copied from the project's docs at github.com/addyosmani/agent-skills

Why you'd want it

Agent Skills is a pack of SKILL.md workflows covering the path from idea to launch, such as spec-driven development, test-driven development, code review, security hardening and shipping, each ending with evidence requirements like passing tests or build output. It also ships reviewer personas, reference checklists and, in Claude Code, slash commands such as /spec, /plan, /build, /test, /review and /ship. It installs with the skills CLI or as a Claude Code, Codex or Gemini CLI plugin, with setup guides for Cursor, Windsurf, OpenCode and GitHub Copilot.

Best for

  • Making agents write specs and tests first
  • Shared engineering standards across several agents
  • Structured code review before merge

Use it when

Your coding agent skips specs, tests or review and you want step-by-step workflows it follows across a project.

Skip it if

Your changes are small one-off edits where a spec, plan and test cycle adds overhead. Installing a single skill with npx leaves out the shared reference checklists.

Related tools

Same category or shared tags.

  1. Spec Kit

    Devtool Standard

    Gives coding agents structured processes for spec-driven builds, bug fixes and idea assessment

    • 141k stars
    • 337 stars/day since creation
    • pushed
    • v1.2.0 on
    • MIT

    Install with uv and create a project

    uv tool install specify-cli
specify init my-project --integration copilot
    Use it when, skip it if, stats for Spec Kit

    Why you'd want it

    The specify CLI installs skills or command files for your coding agent, which you then run in chat: constitution once per project, then specify, plan, tasks, implement and converge for each feature. Optional extensions add a bug-fixing flow (assess, fix, test) and an idea assessment flow that ends in a go, clarify or stop decision, with reports saved as Markdown under .specify/. It has integrations for dozens of agents, including GitHub Copilot, Claude Code, Codex CLI, Cursor, Gemini CLI and Zed, and you can customize it with extensions, presets and workflows.

    Best for

    • Teams that want a spec before code
    • Keeping agent work reviewable step by step
    • Using one process across several coding agents

    Use it when

    You want a coding agent to work from a written specification, plan and task list rather than one prompt, with artifacts you review at each step.

    Skip it if

    Your changes are small enough that a single prompt does the job. The CLI needs Python 3.11+ and uv.

    Stats

    Stars
    141,318
    Last push
    Release
    v1.2.0,
    License
    MIT
    Pricing
    Open source
    Works with
    Claude Code, Cursor, Codex, Gemini CLI, Zed, Linux, macOS, Windows
    Stars per day, since repo creation
    337
    Tier
    Standard, not ranked

    Full stat block for Spec Kit

  2. Rank 1

    universal-modder

    Devtool

    Gives a coding agent skills, a CLI and a shared knowledge base for modding PC games you own

    • score 83
    • 7.7k stars
    • 513 stars/day since creation
    • pushed
    • MIT

    Install as a Claude Code plugin

    /plugin marketplace add rehan-remade/universal-modder
/plugin install universal-modder@universal-modder
    Use it when, skip it if, stats for universal-modder

    Why you'd want it

    universal-modder packages Agent Skills, three subagents and a Python CLI called um that a coding agent uses to mod a game: um scan finds Steam, Epic and Xbox installs and fingerprints the engine, loaders, anti-cheat and save folders, um backup snapshots saves, and um fal, um sprite and um render3d make and fit art, 3D and audio for the engine. The mod-any-game skill runs a fixed loop of recon, a backed-up lab, reading the real code, building one slice, testing it in the running game and writing a field note. Those field notes live in a knowledge base in the repo that agents search with um kb before starting and add to by pull request.

    Best for

    • Modding single-player PC games with an agent
    • Generating sprites and 3D assets for mods
    • Reusing other agents' modding notes

    Use it when

    You want Claude Code, Codex, Gemini CLI or another agent to work out how a game you own is built and ship a mod for it, with assets and an in-game test.

    Skip it if

    You play online games with anti-cheat: its own safety notes say injecting into an online client breaks the game's terms and gets accounts banned, and it refuses to do so. It touches game folders, saves, processes and your mouse and keyboard (asking first), asset generation needs a fal API key or a local ComfyUI server, and the repo is about two weeks old with no tagged release.

    Stats

    Stars
    7,697
    Last push
    Release
    none tagged
    License
    MIT
    Pricing
    Open source
    Works with
    Claude Code, Codex, Gemini CLI, VS Code, Cursor, Windows
    Stars per day, since repo creation
    513
    New and rising score
    83 of 100

    Full stat block for universal-modder

  3. Rank 18

    ccusage

    Devtool

    Reports token usage and costs for Claude Code, Codex and other coding agent CLIs from local data

    • score 44
    • 19k stars
    • 37.7 stars/day since creation
    • pushed
    • v20.0.33 on
    • MIT

    Run with npx

    npx ccusage@latest
    Use it when, skip it if, stats for ccusage

    Why you'd want it

    ccusage reads the usage data that coding agent CLIs store locally and turns it into daily, weekly, monthly and session reports, with per-model breakdowns and separate cache token counts. One report covers Claude Code, Codex, OpenCode, Gemini CLI, GitHub Copilot CLI and more than a dozen other tools, and there are Claude Code extras such as 5-hour billing window reports and a status line integration. Output is a table or JSON, and an offline mode uses cached pricing data.

    Best for

    • Tracking spend across several coding agents
    • Claude Code users watching 5-hour usage windows
    • Exporting usage as JSON for your own dashboards

    Use it when

    You want to see how many tokens and dollars your coding agent sessions use, by day, model, session or project.

    Skip it if

    You need team-wide spend tracking: it only reads local data on the machine where it runs. Costs are calculated from LiteLLM pricing data, not read from your provider bill.

    Stats

    Stars
    19,007
    Last push
    Release
    v20.0.33,
    License
    MIT
    Pricing
    Open source
    Works with
    Claude Code, Codex, Gemini CLI
    Stars per day, since repo creation
    37.7
    New and rising score
    44 of 100

    Full stat block for ccusage

For agents

The same entry, as files an agent can read without scraping this page. 

# read one entry
curl -s https://agenttooldrop.com/tools/addy-agent-skills.md

# list the MCP servers in the catalog
curl -s https://agenttooldrop.com/tools.json \
  | jq -r '.tools[] | select(.category=="mcp-server") | .slug'