Boolean Schemas

Many keywords accept true, false, a schema object, or a builder callback. Boolean values have special meanings.

Object keywords


// additionalProperties
.additionalProperties(false)           // No extra properties allowed
.additionalProperties(true)            // Any extra properties allowed (default)
.additionalProperties((s) => s.string()) // Extra properties must be strings
 
// unevaluatedProperties
.unevaluatedProperties(false)          // No unevaluated properties allowed
.unevaluatedProperties(true)           // Any unevaluated properties allowed
.unevaluatedProperties((s) => s.number()) // Unevaluated must be numbers

Array keywords


// items
.items(false)               // Array must be empty
.items(true)                // Any items allowed
.items((s) => s.string())   // All items must be strings
 
// additionalItems (Draft 7 and earlier)
.additionalItems(false)             // No additional items beyond prefixItems
.additionalItems(true)              // Any additional items allowed
.additionalItems((s) => s.number()) // Additional items must be numbers
 
// unevaluatedItems
.unevaluatedItems(false)             // No unevaluated items allowed
.unevaluatedItems(true)              // Any unevaluated items allowed
.unevaluatedItems((s) => s.string()) // Unevaluated must be strings
 
// contains
.contains(true)                        // Array must have at least one item
.contains(false)                       // Always fails
.contains((s) => s.number().minimum(10)) // Must contain number >= 10

Composition keywords


// not
.not(true)                  // Always fails (not true = false)
.not(false)                 // Always passes (not false = true)
.not((s) => s.string())     // Must not be a string
 
// In anyOf / allOf / oneOf
.anyOf(
  true,                     // Always matches
  (s) => s.string(),
  { type: "number" },       // Plain JSON also works
)

In JSON Schema a boolean is a schema, so any keyword that accepts a schema also accepts a boolean.