webtoolz
A free, open-source, entirely browser-side toolkit of developer utilities — JSON tooling with AI auto-repair, an MCP config generator for 40+ servers, a token counter with cost estimates and a Mermaid editor.
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webtoolz.devAbout webtoolz
webtoolz is a free, open-source collection of developer and creator utilities that all run client-side in the browser — no signups, no uploads, nothing sent to a server. The JSON section is the deepest part of it: format and beautify, validate, diff and compare, convert between formats, build mock APIs, generate share links, and an AI auto-repair mode that takes malformed JSON and fixes it rather than just reporting the parse error. A Mermaid Studio gives a live-preview diagram editor with four themes and unlimited PNG and SVG export, again entirely client-side. The AI section is aimed at people building with large language models and includes a token counter with cost estimates, plus an MCP config generator covering more than forty MCP servers and six AI clients — useful if you have ever hand-written a client config and got the transport or the argument array subtly wrong. There is also an AI Music Studio that generates original songs with AI-written lyrics across sixteen-plus genres with synced lyrics, and a set of media tools. The whole thing is positioned as a toolkit you bookmark rather than an account you create, which for anything involving pasting production JSON or API keys is the meaningful design decision.
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