Skill
Claude
Four Principles
four-principles/
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Four always-on rules for your coding agent: think before coding, keep it simple, change only what was asked, and loop until a check passes.
Four always-on engineering principles the agent applies to every task, not just the big ones.
Why use it
- The agent guesses instead of asking, and picks one reading of an ambiguous request silently.
- It ships 200 lines where 50 would do, and refactors code nobody asked it to touch.
- It says "done" without ever running the check.
What it does
- Think Before Coding: surface assumptions and trade-offs; ask instead of guessing.
- Simplicity First: the minimum that solves the problem; nothing speculative.
- Surgical Changes: every changed line traces to the request; adjacent code stays untouched.
- Goal-Driven Execution: reframe vague asks into checkable ones, then loop until the check passes.
Benefits
- Reviews get fast. Diffs stay small and every line traces to the ask, no archaeology.
- No surprise rewrites. Your untouched code stays untouched.
- "Done" actually means done. Verified, not hoped.
- Drops into any task. One file, every language, zero setup.
Install
Download this skill and copy the four-principles folder to .claude/skills/four-principles/ in your project, or to ~/.claude/skills/four-principles/ to use it in every project. Claude Code finds it on its own; you can also call it with /four-principles.
Part of the Agent Engineering bundle. To get the whole set as a Claude Code plugin: /plugin marketplace add endorphin-ai/hasbrains-agent-kit, then /plugin install agent-engineering@hasbrains-agent-kit.
Source: endorphin-ai/hasbrains-agent-kit. License: MIT.
---
name: four-principles
description: "Four always-on engineering principles for ALL work before, during, and after coding — Think Before Coding (surface assumptions/tradeoffs, never guess silently), Simplicity First (minimum code that solves it, nothing speculative), Surgical Changes (touch only what the request needs, every changed line traces to the ask), and Goal-Driven Execution (define verifiable success criteria, loop until verified). Use on EVERY task that writes, edits, refactors, or fixes code, designs an approach, or interprets a request — not just large features."
---
# Four Engineering Principles
Apply these four principles to **every** task — interpreting a request, designing an approach, writing/editing/refactoring/fixing code, and verifying the result. They are always-on (enforced by rule R6); this is the detailed playbook for the how.
---
## 1. Think Before Coding
Don't assume. Don't hide confusion. Surface tradeoffs.
- State assumptions explicitly. If uncertain, ask.
- If multiple interpretations exist, present them — don't pick silently.
- If a simpler approach exists, say so. Push back when warranted.
- If something is unclear, stop. Name what's confusing. Ask.
## 2. Simplicity First
Minimum code that solves the problem. Nothing speculative.
- No features beyond what was asked.
- No abstractions for single-use code.
- No "flexibility" / "configurability" that wasn't requested.
- No error handling for impossible scenarios.
- If you write 200 lines and it could be 50, rewrite it.
- **Test:** Would a senior engineer say this is overcomplicated? If yes, simplify.
## 3. Surgical Changes
Touch only what you must. Clean up only your own mess.
- Don't "improve" adjacent code, comments, or formatting.
- Don't refactor things that aren't broken.
- Match existing style, even if you'd do it differently.
- If you notice unrelated dead code, mention it — don't delete it.
- Remove imports / variables / functions that YOUR changes made unused.
- Don't remove pre-existing dead code unless asked.
- **Test:** Every changed line should trace directly to the user's request.
## 4. Goal-Driven Execution
Define success criteria. Loop until verified.
Reframe vague asks into verifiable ones:
| Vague ask | Verifiable reframe |
|-----------|--------------------|
| "Add validation" | Write tests for invalid inputs, then make them pass |
| "Fix the bug" | Write a test that reproduces it, then make it pass |
| "Refactor X" | Ensure tests pass before AND after |
For multi-step tasks, state a brief plan with a verify check per step:
```
1. [Step] → verify: [check]
2. [Step] → verify: [check]
3. [Step] → verify: [check]
```
Then execute and loop on each step until its verify check passes. Do not claim a step (or the task) is done until its check actually passes — confirm the evidence, don't assert it.
---
Made by **HasBrains** — https://hasbrains.com/