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Codebase Design Vocabulary

Guides the agent to design deep modules with small interfaces, clean seams, and testable boundaries.

Source Download skill
Repository
mattpocock/skills
Stars
309,658
Licence
MIT
Files
4 files

What it does

Once installed, the agent reviews and plans code structure using a fixed vocabulary from software design: modules, interfaces, seams, depth, leverage and locality. When you ask it to improve how a module is designed, find places to deepen code, or make code easier to test, it aims for a small interface hiding a lot of behaviour and suggests where to place the boundaries between parts. It also points to two companion guides: one for deepening a cluster of code given its dependencies, and one for sketching several radically different interface designs and comparing them.

Great for

  • Developers restructuring a messy codebase who want consistent design reasoning
  • Teams trying to make code easier to test or easier for AI agents to navigate
  • Engineers who want to compare alternative interface designs before writing code

Skip it if

  • Small one-off scripts or simple bug fixes, where this vocabulary adds overhead without much benefit
  • Non-developers, since the skill assumes familiarity with software architecture terms and the agent will use them in its answers

Try asking

  • “Look at the payments module and tell me whether its interface is too shallow, and where the seam should go”
  • “Help me make this order-processing code more testable without rewriting it”
  • “Find deepening opportunities in this package and explain the leverage each would give callers”
  • “Design this API three different ways and compare them on depth and locality”
Step-by-step guide: how to use Codebase Design VocabularyInstall, first run, examples, tips and FAQs

Install in 3 steps

  1. 1

    Download the skill

    The ZIP contains the 4 original files, the MIT licence and an attribution note.

    codebase-design.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip codebase-design.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip codebase-design.zip -d .claude/skills/

    Claude apps (web/desktop): Settings → Capabilities → Skills → Upload skill, and choose the ZIP.

  3. 3

    Ask for the task

    No special command needed — the agent reads the skill's description and loads it when your request matches. Try one of the prompts above.

Get better results

  • Point the agent at a specific module or folder rather than the whole repository, so its suggestions stay concrete.
  • Ask it to run the deletion test on a module to see whether it earns its keep.
  • Review proposed interface changes yourself before applying them, since the skill recommends designs but does not verify them against your real callers.

What's inside

  • agents/openai.yaml
  • DEEPENING.md
  • DESIGN-IT-TWICE.md
  • SKILL.md

Redistributed unmodified from mattpocock/skills under the MIT licence. The assessment was drafted with AI from the skill's files on 2026-10-29. Skills can instruct your agent to run code — read SKILL.md and any scripts before installing.