Does adding contracts slow down my production code?

The skill encourages using static and test-time checks where possible, reserving runtime contracts for untrusted data or safety-critical boundaries to minimize performance impact.

What is the Design-by-Contract (DbC) methodology?

DbC is a programming approach where software components have formal, verifiable interface specifications including preconditions (requirements), postconditions (promises), and invariants (constants).

Which programming languages does this skill support?

The skill provides specialized support for Rust, TypeScript (Zod), Python (icontract), Java/Kotlin (Guava/Built-ins), and C++ (GSL/Boost).

How does the verification hierarchy work?

It follows a principle of using the most efficient check possible: Static Assertions (compile-time) > Test Contracts > Debug Contracts > Runtime Contracts.

Can this skill help fix contract violations?

Yes, it includes a dedicated Remediation phase that diagnoses violation types (Caller fault vs. Callee fault) and suggests targeted code fixes.

Design-by-Contract Development

Name: Design-by-Contract Development
Author: Activer007

byActiver007

0•

Security & Testing

Implements formal contract verification using preconditions, postconditions, and invariants to ensure code correctness and reliability across multiple languages.

This skill enables developers to apply the Design-by-Contract (DbC) methodology within Claude Code, providing a comprehensive workflow for planning, creating, verifying, and remediating software contracts. It allows for the formal specification of component behaviors—defining what a function requires, what it promises, and what state must remain constant—across environments like Rust, TypeScript, Python, and Java. By integrating a verification hierarchy that prioritizes compile-time safety over runtime overhead, this skill helps eliminate architectural bugs, secures API boundaries, and provides automated remediation strategies when contracts are violated.

Key Features

01Phased workflow covering planning, artifact creation, verification, and remediation

02Support for major libraries including Zod, icontract, and Rust's contracts crate

030 GitHub stars

04Automated generation of contract annotations for 8+ programming languages

05Intelligent detection of existing contract patterns and coverage gaps

06Standardized verification hierarchy to optimize performance and safety

Use Cases

01Validating untrusted data at public API and module boundaries

02Ensuring state consistency in safety-critical business logic and financial systems

03Formalizing component expectations to improve team collaboration and documentation

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add activer007/ordinary-claude-skills design-by-contract

For use in Claude.ai and ChatGPT

Download Skill