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.
23 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.
AI Tool Schema Converter
AI & LLM
Convert function-calling schemas between OpenAI, Anthropic, Gemini and MCP.
JSON Schema to AI Tool Schema
AI & LLM
Wrap any JSON Schema into a ready-to-use function-calling tool.
Prompt Diff & Compare
AI & LLM
Compare two prompt versions word by word with a token delta.
LLM Output Diff
AI & LLM
Compare two model responses to measure drift between runs or models.
Context Window Packer
AI & LLM
Fit as many RAG chunks as possible into a model context budget.
AI Dataset Deduplicator
AI & LLM
Remove exact and near-duplicate rows from fine-tuning datasets.
AI Dataset Statistics Analyzer
AI & LLM
Profile a JSONL training set: token stats, roles, duplicates and cost.
Chat Dataset Converter
AI & LLM
Convert between OpenAI chat, ShareGPT, Alpaca and prompt/completion.
Embedding Similarity Calculator
AI & LLM
Cosine, dot product and distance between two embedding vectors.
Embedding Vector Inspector
AI & LLM
Inspect dimensions, norm, mean and spread of an embedding vector.
MCP Tool Schema Generator
AI & LLM
Generate an MCP, OpenAI or Anthropic tool schema from example arguments.