# I Built 6 Free Developer Tools for AI APIs, Cron, Docker, and Self-Hosting > Source: > Published: 2026-05-23 10:02:38+00:00 I keep running into the same friction points: "How much will this prompt cost on GPT-4o vs Claude?", "What's the cron syntax for every Monday at 9am?", "Is there an open-source alternative to Notion I can self-host?" I got tired of Googling each time, so I built a set of free tools that solve these problems. No login, no API keys, no tracking — everything runs in your browser. Here's what each one does. Paste any prompt and instantly see the cost across 10 AI models: GPT-4o, GPT-4o Mini, o3, o4-mini, Claude Sonnet 4, Claude Haiku 4, Gemini 2.5 Pro, Gemini 2.5 Flash, Llama 4 Maverick (via Groq), and DeepSeek R1. It uses tiktoken for exact OpenAI token counts and estimates for other models (~4 chars/token for English, ~1.5 for Chinese). You can adjust monthly call volume and expected output tokens to see projected monthly costs. Try it: AI Prompt Cost Calculator 161 cron expressions covering every common pattern. Each one comes with a plain-English explanation and the next 5 run times. Some examples: */5 * * * * — Every 5 minutes0 * * * * — Every hour0 9 * * 1 — Every Monday at 9:00 AM0 0 1 * * — First day of every monthThere's also a builder mode where you select the schedule and it generates the expression for you. Try it: Cron Expression Generator 36 popular SaaS tools, each with open-source alternatives you can self-host. Some examples: Each alternative has a feature comparison and a link to its Docker deployment config (see tool #4). Try it: Self-Hosted Alternatives One-click Docker Compose configs for 30 self-hosted applications. Copy, edit the environment variables, and run docker compose up -d . Each config includes: Try it: Docker Deploy Generator Compare TTS (text-to-speech) and STT (speech-to-text) pricing across 6 providers: OpenAI, ElevenLabs, Deepgram, AssemblyAI, Google Cloud, and Azure. Enter your expected monthly character volume and see costs for each provider side by side. There are also preset buttons for common volumes (100K, 1M, 5M, 10M characters/month). This was born out of my own frustration trying to compare voice AI pricing — each provider uses different pricing units (per character, per 15 seconds, per minute) making direct comparison painful. Try it: Voice AI Pricing Calculator 18 items across 8 categories for anyone building production AI agents: Each item has a severity level (critical/warning/info) and an explanation of why it matters. Check items off as you go — your progress is saved in localStorage. Try it: AI Agent Safety Checklist All 6 tools are static React apps built with Vite and Tailwind CSS. No backend, no database, no user accounts. Everything runs client-side. The entire collection lives at prompt-cost-calculator-ten.vercel.app with 240 pages total (mostly from the cron generator and its long-tail expressions). I'm working on: Feedback and suggestions welcome. What developer tools are you always Googling for?