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.