specification-generator

specification-generator is a skill for Claude Code, Codex from ArabelaTso/Skills-4-SE. It costs 79 tokens per session (5,712 once invoked), scanned A, original, Apache-2.0.

A tool that creates formal descriptions of code behavior, including required inputs, guaranteed outputs, conditions that always hold, and possible side effects or errors.

In plain words
What is it for?
Use it to generate preconditions, postconditions, invariants, and behavioral contracts for APIs, functions, and classes.
Why use it?
It turns implicit expectations into explicit contracts that are easier to verify, document, and use in design-by-contract development.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to generate preconditions, postconditions, invariants, and behavioral contracts for APIs, functions, and classes.

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Install with agentmods
npx agentmods add skills/arabelatso/skills-4-se/specification-generator
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.

Any agent
npx skills add ArabelaTso/Skills-4-SE --skill specification-generator
Clone the repo
git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE

Made for: Claude Code, Codex.

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 specification-generator

README.md
[![agentmods](https://agentmods.dev/badge/skills/arabelatso/skills-4-se/specification-generator/github.svg)](https://agentmods.dev/skills/arabelatso/skills-4-se/specification-generator)
Your own site
<a href="https://agentmods.dev/skills/arabelatso/skills-4-se/specification-generator"><img src="https://agentmods.dev/badge/skills/arabelatso/skills-4-se/specification-generator/github.svg" alt="Measured on agentmods" height="20"></a>

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 specification-generator

Your own site · 80×15
<a href="https://agentmods.dev/skills/arabelatso/skills-4-se/specification-generator"><img src="https://agentmods.dev/badge/skills/arabelatso/skills-4-se/specification-generator.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 79 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,712 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 pass 7 Sept 2026
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 $0.00079 $0.05712
Opus 5 $0.00039 $0.02856
Sonnet 5 $0.00016 $0.01142
Haiku 4.5 $0.00008 $0.00571

Measured 5d ago against content hash 7c185aa2ffca, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

specification-generator 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 5d 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.

skills/specification-generator/SKILL.md · 921 lines

How it starts

The opening of the file, as written. The whole thing — 921 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Specification Generator

Systematically generate formal specifications from code and requirements. Produces preconditions, postconditions, invariants, and behavioral contracts that enable verification, documentation, and design-by-contract programming.

Core Capabilities

1. Precondition Generation

Define required conditions before execution:

  • Parameter validation - Valid ranges, types, states
  • Object state requirements - Required object states
  • Resource availability - Files exist, connections open
  • Authorization checks - Permission requirements
  • Null safety - Non-null parameter requirements
  • Invariant satisfaction - Class invariants must hold

2. Postcondition Generation

Specify guaranteed outcomes after execution:

  • Return value constraints - Valid return ranges and properties
  • State modifications - How object state changes
  • Side effects - File writes, database updates
  • Exception conditions - When exceptions are thrown
  • Resource management - Resources properly released
  • Invariant preservation - Invariants still hold

3. Invariant Generation

Identify properties that always hold:

  • Class invariants - Properties true for all instances
  • Loop invariants - Properties preserved by iterations
  • Data structure invariants - Consistency conditions
  • Representation invariants - Internal consistency
  • Temporal invariants - Time-based properties

4. Contract Generation

Create complete behavioral specifications:

  • Method contracts - Full pre/post conditions
  • Interface contracts - API behavioral guarantees
  • Type contracts - Type-level properties
  • Protocol contracts - Valid call sequences
  • Frame conditions - What doesn't change

Specification Generation Workflow

Step 1: Analyze Code or Requirements

Understand what needs to be specified:

For existing code:

  • Read function/method implementation
  • Identify parameters and return type
  • Find state modifications
  • Detect resource usage
  • Locate error conditions

Read the full file on GitHub · 921 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. 5d ago First seen · 921 lines · 79 tokens per session scan A 7c185aa2ffca

Subscribe to this mod's changes

specification-generator is a skill published in the GitHub repository ArabelaTso/Skills-4-SE (251 stars, last pushed 19d ago), licensed Apache-2.0. It adds 79 tokens to every session and 5,712 once invoked, about $0.0004 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 2026-09-03.

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