just-works: Skill for Claude Code

.claude/skills/gpt-5-6-prompting/SKILL.md

gpt-5-6-prompting is a skill for Claude Code from Dynokostya/just-works. It costs 135 tokens per session (4,800 once invoked), scanned A, original, Apache-2.0.

A set of instructions for writing prompts for GPT-5.6 models. It covers how to set the desired result, reasoning level, response length, autonomy, approvals, and tool use.

In plain words
What is it for?
Use it when creating, editing, or migrating prompts for GPT-5.6, or when diagnosing changes in how those models follow instructions and perform multi-step work.
Why use it?
It helps prevent prompts from asking for conflicting behaviour or giving the model unsuitable limits. It is intended for GPT-5.6 rather than as a general guide to every model.

Skill for Claude Code

Written for Claude Code: installed under .claude/. Also seen: mentions Codex.

This is Dynokostya/just-works's own configuration. It tells Claude Code how to work on just-works itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything just-works configures →

Reuse

Borrowing it

Nothing to install: this file belongs to Dynokostya/just-works. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/Dynokostya/just-works/main/.claude/skills/gpt-5-6-prompting/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/Dynokostya/just-works

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for gpt-5-6-prompting

README.md
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Your own site
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Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for gpt-5-6-prompting

Your own site · 80×15
<a href="https://agentmods.dev/skills/dynokostya/just-works/gpt-5-6-prompting"><img src="https://agentmods.dev/badge/skills/dynokostya/just-works/gpt-5-6-prompting.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 135 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,800 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 148
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
How audits are shown
Origin original No closer match found 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 5.1 $0.00135 $0.04800
Opus 5 $0.00068 $0.02400
Sonnet 5 $0.00027 $0.00960
Haiku 4.5 $0.00014 $0.00480

Measured 7d ago against content hash 4bdeaac6cc9a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

gpt-5-6-prompting 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 7d ago.

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.

.claude/skills/gpt-5-6-prompting/SKILL.md · 309 lines

How it starts

The opening of the file, as written. The whole thing — 309 lines — stays where its author put it; the contents beside it link to each section on GitHub.

GPT-5.6 Prompt Writing Guidelines

When to Use

  • Creating or editing prompts targeting GPT-5.6 (any variant: gpt-5.6-sol, gpt-5.6-terra, gpt-5.6-luna)
  • Calibrating reasoning effort, verbosity, autonomy boundaries, and tool routing for GPT-5.6 workloads
  • Migrating prompt text from GPT-5.5, GPT-5.4, GPT-5.3-Codex, or older GPT models
  • Diagnosing 5.6-specific behaviors (concise-by-default output, instruction-conflict instability, medium default reasoning, proactive multi-step execution)

Overview

GPT-5.6 is OpenAI's frontier family. gpt-5.6-sol is the flagship (the bare gpt-5.6 alias routes to it); gpt-5.6-terra balances cost; gpt-5.6-luna targets high-volume efficiency. Sol and Terra run ~1.05M-token context with 128K max output; Luna runs 400K context, 128K max output.

Compared with GPT-5.5, it reaches frontier performance with fewer output tokens, is more concise by default, follows prompt contracts more tightly (so conflicting instructions create instability), executes multi-step work more proactively, and has stronger layout and design judgment. New capabilities relevant to prompt design: programmatic tool calling, persisted reasoning across turns, pro mode for quality-first work, and multi-agent coordination (beta).

The core discipline is lean prompting: OpenAI measured 10-15% eval-score improvement with 41-66% token reduction from pruning prompts — GPT-5.6 rewards removing scaffolding more than adding it.

  • Outcome-first: Strongest when the prompt defines destination, constraints, evidence, and completion bar, then leaves the path to the model.
  • Tight contract-following: Follows prompt contracts closely; duplicated or conflicting instructions destabilize behavior. State each instruction once.
  • Concise by default: More concise than GPT-5.5 — carried-over brevity blocks can now cut content you need. Define what brief answers must include.
  • Proactive and persistent: Carries multi-step tasks forward on its own; needs approval boundaries, not step-by-step supervision.
  • Strong planning over tools: Needs less fallback and invocation scaffolding than 5.5; still benefits from explicit prerequisite-retrieval and routing rules.
  • Stronger design judgment: Better layout, hierarchy, and visual taste — constrain it to the existing design system rather than prescribing layout steps.
  • Legacy-prompt penalty: Process-heavy stacks carried from older models narrow the search space and waste tokens.

Read the full file on GitHub · 309 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. 7d ago First seen · 309 lines · 135 tokens per session scan A 4bdeaac6cc9a

Subscribe to this mod's changes

gpt-5-6-prompting is a skill published in the GitHub repository Dynokostya/just-works (14 stars, last pushed 3d ago), licensed Apache-2.0. It adds 135 tokens to every session and 4,800 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-04.

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