← ReferenceJSON SchemaWhere JSON Schema fits in JsonUI today: the spec-file schemas ship inside the jsonui-helper VS Code extension, Layout JSON is validated by the toolchain itself, and no standalone schema files are published for download yet.in-editor today
What exists todayTwo spec schemas exist — `screen_spec_schema.json` and `component_spec_schema.json` — vendored inside jsonui-helper and matched to `*.spec.json` files. There is no JSON Schema for Layout JSON: the layout grammar's source of truth is the SSoT attribute table (`attribute_definitions.json`) that `jui build` validates against, and this site's attribute reference is generated from the same table.
Editor support todayVS Code: install jsonui-helper — it registers the two spec schemas for `*.spec.json` automatically, no `$schema` key needed. Other editors have no packaged integration today; validation there comes from running `jui build` and the MCP `doc_validate_spec` tool rather than from editor-side schema checks.
Runtime vs editor validationFor `*.spec.json`, jsonui-helper's schema checks catch shape mistakes — typos, missing required fields, wrong types — before you save. Semantic checks ('custom type is not in the whitelist', 'binding refers to a uiVariable that does not exist') land in `jui verify` and the MCP `doc_validate_spec` tool, and Layout JSON is checked by `jui build`'s validators. Editor validation is fast and local; toolchain validation is authoritative and catches the things schema alone cannot.
VersioningThe vendored schemas version with the jsonui-helper release that bundles them — updating the extension updates the schemas. There are no separately versioned public schema URLs today; if standalone publication ships later, it will be announced here.
Keep reading
Attribute referenceThe human-facing cousin of the schema./reference/attributes
Why spec-firstWhy schema-first editing pays for itself./concepts/why-spec-first