Open-source tool claims 97 per cent token savings for AI agents
Developer activeing123 releases token-efficient CLI client designed to reduce syntax costs in AI interactions
A new open-source command-line interface tool named Mcptoon has been released on GitHub, aiming to address the growing inefficiency of token consumption in artificial intelligence workflows. Developed by activeing123, the utility is a client for the Model Context Protocol (MCP) that utilises a format called TOON (Token-Optimized Object Notation) to significantly reduce the data overhead associated with standard JSON.
The release, announced via a Show HN post on Hacker News, claims that Mcptoon reduces token usage by 97 per cent during tool discovery and between 40 and 60 per cent for results compared to conventional methods. According to the developer, standard JSON syntax can consume between 30 and 55 per cent of a 128K context window, with the majority of that space dedicated to syntax rather than actual data content. Mcptoon reportedly reduces the token cost for tool discovery from over 10,000 tokens to approximately 350.
Mcptoon is a pure Python utility requiring Python 3.10 or higher, with zero third-party dependencies. The source code comprises approximately 1,700 lines and is designed to be cross-platform, supporting Windows, macOS, and Linux. The tool connects to any MCP server via stdio or HTTP and outputs TOON format, which the developer states retains all information while minimising byte size.
The client is designed to be compatible with various AI agents that can execute shell commands, including Claude Code, Codex, OpenCode, Cursor, and CatPaw. Configuration is managed through a global settings file at ~/.mcptoon/config.json, with the option for project-level overrides at ./.mcptoon.json. Users can also set the environment variable MCPTOON_AGENT_TYPE=claude to automatically select the TOON flag for every call.
Safety features are built into the utility, which blocks operations matching dangerous patterns such as delete, drop, purge, wipe, and kill unless the user explicitly passes the --destructive flag. Usage data is stored locally at ~/.cache/mcptoon/usage.json and is never transmitted externally. The developer has clarified that Mcptoon is an independent third-party client and is not affiliated with Anthropic or other major AI providers.
