P14b-validassert

A set of coding and review guidelines for writing simpler, easier-to-test software. It favors plain data, small focused functions, clear call sites, and early design decisions while allowing the existing codebase to take priority.

In plain words
What is it for?
Use it while designing features, implementing code, writing tests, reviewing a change or pull request, and checking work before committing or pushing it.
Why use it?
It helps prevent tangled designs and unclear interfaces before they become expensive to change.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/gitrasheed/metis-skill/p14b-validassert
Any agent
npx skills add gitRasheed/metis-skill --skill p14b-validassert
Clone the repo
git clone --depth 1 https://github.com/gitRasheed/metis-skill

Made for: Claude Code, Codex.

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,267 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 77% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.03267
Opus 5 $0.00000 $0.01633
Sonnet 5 $0.00000 $0.00653
Haiku 4.5 $0.00000 $0.00327

Measured yesterday against content hash 299deab0eedb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

P14b-validassert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

77% identical to metis — 39 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

evals/cases-v5/skill-permutations/P14b-validassert/SKILL.md · 178 lines

How it starts

The opening of the file, as written. The whole thing — 178 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Metis

Write code that favors plain data, pure logic, clear call sites, and early architectural thinking. These are strong defaults, not rigid laws: follow the surrounding codebase, framework constraints, and language norms when they clearly matter more.

Apply sections by phase instead of holding everything at once:

  • Designing or starting a task: Design principles, LLM agent process
  • Implementing: Working rules, Implementation rules, plus the SOLID checklist for non-trivial modules
  • Writing tests: Testing checklist
  • Reviewing a diff or PR: Code review mode
  • Before claiming done, committing, or pushing: Final verification checklist

Design principles

  1. Start from the call site, by wishful thinking: pretend the perfect helpers already exist, name them the way you would want to call them, and get the top-level usage reading cleanly. If the calling code reads awkwardly, the abstractions are wrong — and you find out before building anything.
  2. Prefer plain data plus focused functions, modules, or systems over behavior-heavy objects. Draw boundaries around what systems do, not what entities are.
  3. Choose the simplest state model that matches reality: discriminated unions for mutually exclusive states, composable data for orthogonal features, and a plain flat record when neither pressure exists — do not over-architect the simple case.
  4. Isolate mutation and I/O near the edges. Orchestration decides what happens; inner helpers do narrow, understandable work.
  5. Push ifs up, fors down. Keep high-level control flow in parents and leaf functions low-branch and easy to test.
  6. Validate untrusted data where it crosses a trust boundary — parsing, persistence, external APIs — and assert internal invariants whose failure would mean a programming error: state transitions, function contracts. Check what must be true and, when useful, what must not be.
  7. Prefer explicit, behavior-focused tests without indirection that hides intent.
  8. Sanity-check the likely bottleneck first — network, disk, memory, then CPU. Prefer architecture changes over late micro-optimizations.
  9. Design for the hardest real requirement first, then simplify downward. Do not architect for the easy case and try to scale it up later.
  10. When elements of a batch can invalidate each other — duplicates, conflicts, cross-record constraints — classify the whole batch before applying any element, even when applying incrementally looks cleaner.

Read the full file on GitHub · 178 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 178 lines · 0 tokens per session scan A 299deab0eedb

Subscribe to this mod's changes

P14b-validassert is a skill published in the GitHub repository gitRasheed/metis-skill (2 stars, last pushed 10d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 3,267 tokens. A static security scan graded it A with 0 findings. It is 77% identical to metis, differing in 39 lines, and is treated as a copy.