Best AI & LLM Tools
A hand-checked list of the best free ai & llm tools for developers. Every tool runs in your browser — no upload, no login, no API key.
12 tools
AI Token Counter
AI & LLM
Count exact LLM tokens for GPT, Claude and Gemini prompts.
LLM Context Window Calculator
AI & LLM
See if your system, context and user messages fit the model window.
LLM API Cost Calculator
AI & LLM
Estimate GPT, Claude and Gemini API spend per call and per month.
Prompt Linter
AI & LLM
Audit prompts for vague wording, missing formats and leaked secrets.
JSONL Validator
AI & LLM
Validate JSONL and fine-tuning datasets line by line.
JSONL Formatter
AI & LLM
Pretty-print, minify, sort and deduplicate JSON Lines files.
JSONL ↔ JSON Converter
AI & LLM
Convert JSON Lines to a JSON array and back again.
RAG Text Chunker
AI & LLM
Split documents into token-sized overlapping chunks for embedding.
LLM Structured Output Validator
AI & LLM
Check that a model's JSON reply matches your JSON Schema.
AI Tool Schema Builder
AI & LLM
Build function-calling schemas for OpenAI, Claude, Gemini, MCP and the AI SDK.
MCP Tool Schema Validator
AI & LLM
Validate Model Context Protocol tool definitions before you ship them.
AI PII & Secret Redactor
AI & LLM
Strip emails, keys, tokens and personal data before prompting an LLM.