JSON Schema Compliance

The validator ensures every generated value matches its declared primitive type. A field defined as "type": "integer" will reject "42" (a string) or 42.0 (a float). This prevents silent type coercion bugs that corrupt downstream databases and API contracts.

• String: Must be a valid UTF-8 sequence
• Number/Integer: Strict numeric parsing, no scientific notation unless allowed
• Boolean: Only true or false, rejects "true" or 1
• Null: Explicitly handled via "type": "null" or nullable combinators

A required array defines the non-negotiable keys that must exist in the generated object. If a model omits a mandatory field like "email" in a user profile schema, the output is immediately rejected before it enters any data pipeline.

• Validates root-level and nested object properties
• Catches omissions that would cause KeyError or NullPointerException in consuming services
• Works in tandem with "minProperties" and "maxProperties" for structural completeness

Beyond type checking, JSON Schema applies quantitative boundaries to values. A model generating a product price must respect "minimum": 0 and "exclusiveMaximum": 10000. String lengths, array sizes, and numeric ranges are all enforceable.

• Strings: minLength, maxLength, pattern (regex)
• Numbers: minimum, maximum, multipleOf
• Arrays: minItems, maxItems, uniqueItems
• Objects: minProperties, maxProperties

The enum keyword restricts a field to an explicit set of acceptable values, creating a controlled vocabulary. For a sentiment analysis output, "enum": ["positive", "negative", "neutral"] prevents the model from inventing labels like "mostly_good" that would break analytics dashboards.

• const locks a single immutable value
• Prevents semantic drift in categorical fields
• Essential for maintaining referential integrity in database writes

Schemas define hierarchical object graphs using $defs and $ref for recursive or reusable components. A blog post schema might reference a reusable author definition, ensuring consistent sub-object structure across all generated content without duplication.

• $ref: Points to a definition by URI fragment (e.g., #/$defs/address)
• $defs: A local registry of reusable schema components
• Prevents structural inconsistency in deeply nested JSON payloads

The format keyword applies semantic checks beyond syntax. A field with "format": "date-time" must be a valid RFC 3339 timestamp, not just any string. This catches logically invalid data that passes type checks but fails business logic.

• "date-time": ISO 8601 timestamps
• "email": RFC 5322 compliant addresses
• "uri": Valid absolute or relative URIs
• "uuid": Universally unique identifier format
• "ipv4" / "ipv6": Network address validation