Diagram Design

Why it's ranked here

The build quality stands out for a project born from one person's daily annoyance. Every visual grammar ships alongside its own automated checker, and each checker has its own adversarial test suite, all wired into continuous integration across three operating systems. Design decisions are recorded and revisited in dated records, not asserted. MIT licensing and a governance file that names exactly which changes require human sign-off, including security disclosures and merge authorization, reinforce that this is maintained like production software, not a demo skill.

What's good

The generated files carry no scripting by default, so a diagram dropped into a shared doc or a blog post is not itself an attack surface. When motion is requested, the one allowed animation block is checked against a fixed, reviewed original by a cryptographic hash, so nothing bespoke sneaks in. Structural checks catch failures a visual skim misses: a text label rendered behind a box, duplicate or dangling identifiers in a block diagram, a missing name on a cited component. The checking tools themselves depend on nothing beyond the Python standard library.

Tradeoffs

Contributing here is a heavier lift than it looks: a pull request must pass several dozen separate validation commands locally before it is considered ready, covering everything from color and font conformance to flow-conservation math for individual chart types. Manifest version numbers are bumped automatically after merge and forbidden in the pull request itself, which keeps merges clean but adds one more rule newcomers have to learn. The tool is also useless on its own: it only runs inside a compatible agent host, never as an independent program.

How to use it well

Reach for this when writing technical documentation, a blog post, or a proposal that needs a real diagram and no designer is available. Point it at an existing site once to lock in brand colors and type, then reuse that saved profile across every later diagram so results stay consistent. It is not the right choice for a one-off scribble, a diagram that needs live interactivity beyond the single built-in animation, or content that a plain table would explain just as well.

Observed

License

MIT

Distribution

Packaged as a Claude Code / Codex / Factory Droid / Pi plugin, installed via a marketplace-add and plugin-install command pair

Interfaces

Invoked as a conversational agent skill, plus two dedicated slash commands for exporting to SVG/PNG and importing Mermaid sources

Output format

Self-contained HTML files with inline SVG and CSS; no external JavaScript in the default static mode

Import formats supported

draw.io, Mermaid, and Excalidraw source files

Validation tooling language

Python, standard-library only (uses html.parser, argparse, dataclasses) for the linting and verification scripts

Test layout

No separate tests directory; test scripts sit alongside the verification scripts they cover in the scripts folder

Runtime requirement

Python 3.10 or newer for the development and validation scripts

Platform coverage

Continuous integration runs across Linux, Windows, and macOS