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JSON Contract Lab

Paste generated JSON and check its syntax, required keys and field types. Try a deliberate mismatch to see exactly which fields fail.

Try the appOpen in StudioRead the HOWTO
JSON Contract Lab with illustrative sample records
Actual AppSPEC output with an illustrative JSON input.

Try this workflow

  1. Click Check JSON to validate the example against the visible field contract.
  2. Click Try a mismatch, check it, and read the missing-field and unexpected-key errors. Edit the JSON to resolve them.
  3. Open the spec in Studio to change SHAPE. All fields are required; nested objects and arrays are checked only for their top-level type. Values stay in memory and are not sent or saved.

Input stays in memory and is not sent or saved.

The AppSPEC

<?xml version="1.0" encoding="UTF-8"?>
<APP ID="json-contract-lab" NAME="JSON Contract Lab" THEME="modern-minimal" WIDTH="1240px">
  <DATA MODE="local" />
  <STATE ID="check" NAV="Contract checker" ICON="braces">
    <TEXT STYLE="h1" TEXT="Catch data errors before they reach your UI" />
    <TEXT STYLE="muted" TEXT="Check generated JSON for syntax, required fields, unexpected keys and wrong top-level types before passing it to an application." />
    <JSON-CHECK SHAPE="title:string,priority:string,done:boolean" LABEL="Generated JSON" VALUE="{&quot;title&quot;:&quot;Review generated output&quot;,&quot;priority&quot;:&quot;high&quot;,&quot;done&quot;:false}" />
    <TEXT STYLE="small" TEXT="Nothing is sent or saved. A passing contract checks structure, not truth or authorization." />
  </STATE>
</APP>