Free AI & LLM Developer Tools
Small utilities for working with language models: size a prompt, estimate what a request costs, rescue broken JSON, mask secrets and prepare text for retrieval. They need no API key and make no model calls; your input stays in your browser.
Prompts, tokens and cost
Estimate how much text fits in a context window, price a request from rates you enter, and build prompts from reusable templates. Token counts are estimates, not exact tokenizer output.
LLM Token Counter
Estimate prompt tokens, words and characters locally to plan context-window use before sending text to a language model.
Open tool AI & LLM ToolsAI API Cost Calculator
Turn input and output token counts and per-million prices you enter into per-request and multi-request cost estimates.
Open tool AI & LLM ToolsPrompt Template Builder
Write a prompt with {{variables}}, fill the detected fields or paste JSON values, and copy the finished prompt. Plain replacement only.
Open toolStructured data from models
Clean up JSON that a model wrapped in prose or Markdown, then describe its shape with a draft JSON Schema. Repaired JSON is valid syntax, not necessarily correct data.
LLM JSON Repair
Fix common invalid JSON from language models: Markdown fences, surrounding prose, trailing commas and smart quotes, without guessing.
Open tool AI & LLM ToolsJSON to JSON Schema Generator
Generate a draft JSON Schema from a sample JSON document, with nested objects, arrays and an optional required-fields toggle.
Open tool AI & LLM ToolsMCP Config Generator
Generate a basic mcpServers JSON configuration for a Model Context Protocol server with command, args, environment placeholders or a URL.
Open toolRetrieval and privacy
Split documents into overlapping chunks for retrieval experiments and mask common sensitive patterns before sharing text with an assistant. Automatic redaction can miss sensitive information.
RAG Text Chunker
Split text into overlapping chunks by characters, words or estimated tokens for retrieval-augmented generation, and copy any chunk.
Open tool AI & LLM ToolsAI Prompt Redactor
Mask emails, phone numbers, IP addresses, tokens, API-key-like strings and card-like numbers in a prompt before sharing it.
Open toolRelated developer tools
Model output is usually JSON, so the JSON Formatter andJSON Minifier fit naturally after a repair. Turn a sample into types with JSON to Dart, convert configuration withYAML to JSON, or inspect tokens with theJWT Decoder. Browse the complete directory or the developer tools collection.