AI EngineerGuide

Free tools for AI engineers

Small, single-purpose tools for people building with LLM APIs.

Every tool runs in your browser. No signup, nothing uploaded.

Model migrations

Request migration linterPaste an API request, pick the target model, and see every field that will return a 400. Deprecated model-ID scannerPaste code, config or an n8n workflow and find every retiring or retired model ID. Model retirement calendarEvery upcoming OpenAI, Claude and Gemini API shutdown, with days left and replacements.
Prompt migration check (BYOK)soonRun your prompts on the old and new model side by side with your own API key.

Tokens, cost and context

LLM API cost calculatorMonthly cost across models, plus token counts, context fit, prompt caching and old-vs-new model diffs. Token counterExact OpenAI token counts and Claude and Gemini estimates, with cost per model.

Building with LLM APIs

Structured output schema checkerCheck a JSON Schema for OpenAI strict mode, Claude strict tools and Gemini, and convert tool definitions.

Why these tools

Each tool does one job and runs in your browser, so you can paste real prompts, schemas and configs without sending them anywhere. Prices, limits and retirement dates come from official provider pages, a daily job refreshes them, and each tool links to the pages its data comes from.

If you need a tool that isn’t here, email me and tell me what you’d use it for.