json-ui-schemas

name	json-ui-schemas
description	JSON schemas for Fused canvas UI widget components (text, input, button, dropdown, charts, maps, sql-table, form, transformer, etc.). Use when authoring or editing widget JSON files (e.g. `widget_*.json` in canvas directories), validating widget props, or answering questions about which fields a given widget type accepts.

Fused JSON UI widget schemas

Reference for every supported widget type and its prop schema.

The full JSON Schema for each component (with descriptions, defaults, required fields, and enum values) lives in reference.md next to this file. Read it before authoring or modifying widget JSON.

Available widget types

• Layout / containers: div, form, sql-runner (children: yes)
• Inputs: input, dropdown, slider, button, code-editor
• Display: text, image, big-number, iframe
• Charts: bar-chart, line-chart, stacked-bar-chart, stacked-area-chart, scatter-chart, donut-chart, heatmap-chart
• Tables: sql-table
• Maps: map, map-bounds, map-h3, fused-map
• Meta / advanced: widget-builder, transformer, ai-chat

Common conventions

• param syncs a widget's value with a canvas parameter (or a form field when nested in form).
• sql fields accept DuckDB queries with {{udf_name}} and $param_name placeholders. Required output columns vary by widget — check the schema.
• style is always a CSS string ("padding: 8px; color: red"), not an object.
• Charts default barColor/lineColor to Fused lime yellow (#E8FF59).

How to use this skill

1. Open reference.md and find the section for the widget type you're working with.
2. Honor required props and respect enum constraints.
3. When constructing a widget JSON, prefer SQL-driven options/data over static when a UDF is available.
4. Validate output against the schema's additionalProperties: false — unknown keys will be rejected.

Debugging widgets with the Fused CLI

The fused json-ui subcommands are the fastest way to check your work without round-tripping through the canvas UI. See the fused:fused-cli skill for full flag details; the common debugging flow is:

• Verify the schema you're targeting — fused json-ui schemas <type> prints the live JSON Schema for one or more component types (or all of them if omitted). Use this when reference.md and the CLI disagree; the CLI is authoritative.
• Validate a widget JSON before pushing — fused json-ui validate path/to/widget_foo.json (or a path to a .json5 file, or an inline JSON5 string). Run this after every non-trivial edit; it catches missing required props, unknown keys, and bad enum values without needing a canvas push.
• See a widget rendered without opening a browser tab — once the canvas is shared (fused canvas share <ref>), use fused json-ui run-shared-widget <share-token> <widget-name> --screenshot-filename out.png to render the widget headlessly and save a PNG. Add --wait N if the widget loads data asynchronously. run-inline-widget does the same for an inline JSON5 config string, which is useful for iterating on a widget that isn't committed yet.
• Refresh the catalog — fused json-ui catalog-prompt prints the high-level component catalog; handy when a new widget type appears in the CLI before it lands in reference.md.

Recommended loop when authoring a new widget JSON: write → fused json-ui validate <file> → fix → push → fused json-ui run-shared-widget to confirm it renders.