🧰 I Built LLMKit: A Complete Toolkit for Testing LLM APIs

Source: Dev.to

Tired of switching between Postman, documentation, and code editors when testing LLM APIs? I built a solution. 🚀

As a developer working with AI integrations, I was constantly:

• Testing Claude on different providers (Anthropic vs third‑party)
• Writing the same API code over and over
• Comparing model responses manually
• Sharing configurations via screenshots 😅

I built a Next.js app that handles everything in one place.

Features

Built With

• Framework: Next.js 14 with App Router
• Language: TypeScript for type safety
• Styling: Tailwind CSS + Shadcn/ui components
• Theme: Professional dark/light mode with orange accents

The app automatically generates production‑ready API integration code in JavaScript, Python, and cURL formats. Just select your model and provider, and get copy‑paste‑ready implementations.

Share your exact testing setup via URL parameters—perfect for team collaboration and documentation. Real‑time metrics include response time, token usage, and cost estimation for every API call.

Key Insights from Building LLMKit

• Start simple – Over‑engineered state management initially slowed progress.
• Mobile matters – More mobile users than expected; implemented tab‑based navigation for small screens.
• TypeScript saves time – Caught bugs early in development.
• User feedback is gold – Early testers revealed UX issues that guided improvements.
• CORS issues – Resolved with Next.js API routes acting as a proxy.
• API key security – Kept keys client‑side only with clear warnings.

Live Demo

🔗 https://llmkit.cc

Perfect For

• API developers testing integrations
• Teams comparing model performance
• Startups evaluating AI providers
• Anyone learning LLM APIs

Roadmap (Planned)

• User authentication & saved configs
• Team collaboration features
• API usage analytics
• Streaming response support

Call to Action

Built this because I needed it. Turns out other developers did too!

What tools do you use for API testing? 👇