migrating-json-schemas

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Translated

Migrates JSON Schemas between draft versions for use with z-schema. Use when the user wants to upgrade schemas from draft-04 to draft-2020-12, convert between draft formats, update deprecated keywords, replace id with $id, convert definitions to $defs, migrate items to prefixItems, replace dependencies with dependentRequired or dependentSchemas, adopt unevaluatedProperties or unevaluatedItems, or adapt schemas to newer JSON Schema features.

4installs

Sourcezaggino/z-schema

Added on2026-02-27

NPX Install

npx skill4agent add zaggino/z-schema migrating-json-schemas

SKILL.md Content

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Migrating JSON Schemas Between Drafts

z-schema supports draft-04, draft-06, draft-07, draft-2019-09, and draft-2020-12. This skill covers migrating schemas between drafts and verifying them with z-schema.

Migration workflow

Identify the source draft (check
```
$schema
```
or
```
id
```
/
```
$id
```
usage).

Set the target version on the validator:

typescript

import ZSchema from 'z-schema';
const validator = ZSchema.create({ version: 'draft2020-12' });

Run
```
validator.validateSchema(schema)
```
to surface incompatibilities.
Fix each reported error using the keyword mapping below.
Re-validate until the schema passes.

Quick reference: keyword changes

Old keyword (draft-04)	New keyword (draft-2020-12)	Introduced in
`id`	`$id`	draft-06
`definitions`	`$defs`	draft-2019-09
Array-form `items` (tuple)	`prefixItems`	draft-2020-12
`additionalItems`	`items` (when `prefixItems` present)	draft-2020-12
`exclusiveMinimum: true` (boolean)	`exclusiveMinimum: <number>`	draft-06
`exclusiveMaximum: true` (boolean)	`exclusiveMaximum: <number>`	draft-06
`dependencies` (string arrays)	`dependentRequired`	draft-2019-09
`dependencies` (schema values)	`dependentSchemas`	draft-2019-09
`$recursiveRef` / `$recursiveAnchor`	`$dynamicRef` / `$dynamicAnchor`	draft-2020-12

For the complete keyword mapping with examples, see references/keyword-mapping.md.

Common migration paths

Draft-04 → Draft-2020-12

This is the largest jump. Apply changes in order:

1. Rename
id
to
$id

json

// Before (draft-04)
{ "id": "http://example.com/person.json", "type": "object" }

// After (draft-2020-12)
{ "$id": "http://example.com/person.json", "type": "object" }

2. Convert boolean
exclusiveMinimum
/
exclusiveMaximum
to numeric

json

// Before (draft-04)
{ "type": "number", "minimum": 0, "exclusiveMinimum": true }

// After (draft-2020-12)
{ "type": "number", "exclusiveMinimum": 0 }

Note: the

minimum

keyword is removed when converting to

exclusiveMinimum

as a number, since

exclusiveMinimum: 0

means "greater than 0".

3. Rename
definitions
to
$defs

json

// Before
{ "definitions": { "address": { "type": "object" } } }

// After
{ "$defs": { "address": { "type": "object" } } }

Update all

$ref

values that point to

#/definitions/...

→

#/$defs/...

.

4. Split
dependencies

json

// Before (draft-04) — mixed dependencies
{
  "dependencies": {
    "billing_address": ["credit_card"],
    "credit_card": { "type": "object", "properties": { "cvv": { "type": "string" } } }
  }
}

// After (draft-2020-12) — split into two keywords
{
  "dependentRequired": {
    "billing_address": ["credit_card"]
  },
  "dependentSchemas": {
    "credit_card": { "type": "object", "properties": { "cvv": { "type": "string" } } }
  }
}

5. Convert tuple
items
to
prefixItems

json

// Before (draft-04)
{
  "type": "array",
  "items": [{ "type": "string" }, { "type": "number" }],
  "additionalItems": false
}

// After (draft-2020-12)
{
  "type": "array",
  "prefixItems": [{ "type": "string" }, { "type": "number" }],
  "items": false
}

When

items

was an array (tuple validation), it becomes

prefixItems

. The old

additionalItems

becomes

items

.

6. Add
$schema
declaration

json

{ "$schema": "https://json-schema.org/draft/2020-12/schema" }

Draft-07 → Draft-2020-12

Smaller jump. Main changes:

```
definitions
```
→
```
$defs
```
(and update
```
$ref
```
paths)
Array-form
```
items
```
→
```
prefixItems
```
```
additionalItems
```
→
```
items
```
(when
```
prefixItems
```
present)

dependencies

→

dependentRequired

/

dependentSchemas

Consider adopting
```
unevaluatedProperties
```
/
```
unevaluatedItems
```
for stricter validation of combined schemas

Draft-2019-09 → Draft-2020-12

Minimal changes:

Array-form
```
items
```
→
```
prefixItems
```
,
```
additionalItems
```
→
```
items
```

$recursiveRef

/

$recursiveAnchor

→

$dynamicRef

/

$dynamicAnchor

Verifying a migrated schema

After migration, validate the schema itself against the target draft's meta-schema:

typescript

import ZSchema from 'z-schema';

const validator = ZSchema.create({ version: 'draft2020-12' });

try {
  validator.validateSchema(migratedSchema);
  console.log('Schema is valid for draft-2020-12');
} catch (err) {
  console.log('Schema issues:', err.details);
}

Then test data validation to confirm behavior is unchanged:

typescript

// Test with known-good data
validator.validate(knownGoodData, migratedSchema);

// Test with known-bad data
const { valid } = validator.validateSafe(knownBadData, migratedSchema);
if (valid) {
  console.warn('Migration issue: previously invalid data now passes');
}

Backward compatibility

If schemas must work across multiple draft versions, use

version: 'none'

and set

$schema

in each schema to declare its own draft:

typescript

const validator = ZSchema.create({ version: 'none' });

Reference files

references/keyword-mapping.md — Complete keyword mapping across all drafts with before/after examples

migrating-json-schemas

NPX Install

Tags

SKILL.md Content

Migrating JSON Schemas Between Drafts

Migration workflow

Quick reference: keyword changes

Common migration paths

Draft-04 → Draft-2020-12

Draft-07 → Draft-2020-12

Draft-2019-09 → Draft-2020-12

Verifying a migrated schema

Backward compatibility

Reference files