support http://json-schema.org/draft-07/schema#

jsonschema/doc.go

@@ -6,8 +6,8 @@
 Package jsonschema is an implementation of the [JSON Schema specification],
 a JSON-based format for describing the structure of JSON data.
 The package can be used to read schemas for code generation, and to validate
-data using the draft 2020-12 specification. Validation with other drafts
-or custom meta-schemas is not supported.
+data using the draft 2020-12 and draft-07 specifications. Validation with
+other drafts or custom meta-schemas is not supported.
 
 Construct a [Schema] as you would any Go struct (for example, by writing
 a struct literal), or unmarshal a JSON schema into a [Schema] in the usual

jsonschema/schema.go

@@ -20,10 +20,10 @@ import (
 )
 
 // A Schema is a JSON schema object.
-// It corresponds to the 2020-12 draft, as described in https://json-schema.org/draft/2020-12,
-// specifically:
-// - https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-01
-// - https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-validation-01
+// It supports both draft-07 and the 2020-12 draft specifications:
+//   - Draft-07: http://json-schema.org/draft-07/schema#
+//   - Draft 2020-12: https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-01
+//     and https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-validation-01
 //
 // A Schema value may have non-zero values for more than one field:
 // all relevant non-zero fields are used for validation.
@@ -104,6 +104,9 @@ type Schema struct {
 	PropertyNames         *Schema             `json:"propertyNames,omitempty"`
 	UnevaluatedProperties *Schema             `json:"unevaluatedProperties,omitempty"`
 
+	// draft-07 specific - Dependencies field that was split in draft 2020-12
+	Dependencies map[string]any `json:"dependencies,omitempty"`
+
 	// logic
 	AllOf []*Schema `json:"allOf,omitempty"`
 	AnyOf []*Schema `json:"anyOf,omitempty"`
@@ -176,11 +179,24 @@ func (s *Schema) MarshalJSON() ([]byte, error) {
 	case s.Types != nil:
 		typ = s.Types
 	}
+
+	// For draft-07 compatibility: if we only have PrefixItems and no Items,
+	// marshal PrefixItems as "items" array, otherwise marshal Items as single schema
+	var items any
+	if len(s.PrefixItems) > 0 && s.Items == nil {
+		// This looks like a draft-07 items array converted to prefixItems
+		items = s.PrefixItems
+	} else if s.Items != nil {
+		items = s.Items
+	}
+
 	ms := struct {
-		Type any `json:"type,omitempty"`
+		Type  any `json:"type,omitempty"`
+		Items any `json:"items,omitempty"`
 		*schemaWithoutMethods
 	}{
 		Type:                 typ,
+		Items:                items,
 		schemaWithoutMethods: (*schemaWithoutMethods)(s),
 	}
 	return marshalStructWithMap(&ms, "Extra")
@@ -202,6 +218,7 @@ func (s *Schema) UnmarshalJSON(data []byte) error {
 
 	ms := struct {
 		Type          json.RawMessage `json:"type,omitempty"`
+		Items         json.RawMessage `json:"items,omitempty"`
 		Const         json.RawMessage `json:"const,omitempty"`
 		MinLength     *integer        `json:"minLength,omitempty"`
 		MaxLength     *integer        `json:"maxLength,omitempty"`
@@ -267,6 +284,34 @@ func (s *Schema) UnmarshalJSON(data []byte) error {
 	set(&s.MinContains, ms.MinContains)
 	set(&s.MaxContains, ms.MaxContains)
 
+	// Handle "items" field: can be either a schema or an array of schemas (draft-07)
+	if len(ms.Items) > 0 {
+		switch ms.Items[0] {
+		case '{':
+			// Single schema object
+			err = json.Unmarshal(ms.Items, &s.Items)
+		case '[':
+			// Array of schemas (draft-07 tuple validation)
+			// For draft-07, convert items array to prefixItems for compatibility
+			err = json.Unmarshal(ms.Items, &s.PrefixItems)
+		case 't', 'f':
+			// Boolean schema
+			var boolSchema bool
+			if err = json.Unmarshal(ms.Items, &boolSchema); err == nil {
+				if boolSchema {
+					s.Items = &Schema{}
+				} else {
+					s.Items = falseSchema()
+				}
+			}
+		default:
+			err = fmt.Errorf(`invalid value for "items": %q`, ms.Items)
+		}
+		if err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 
@@ -342,6 +387,7 @@ func (s *Schema) everyChild(f func(*Schema) bool) bool {
 			}
 		}
 	}
+
 	return true
 }
 

jsonschema/validate.go

@@ -20,15 +20,34 @@ import (
 	"github.com/modelcontextprotocol/go-sdk/internal/util"
 )
 
-// The value of the "$schema" keyword for the version that we can validate.
-const draft202012 = "https://json-schema.org/draft/2020-12/schema"
+// The values of the "$schema" keyword for the versions that we can validate.
+const (
+	draft07     = "http://json-schema.org/draft-07/schema#"
+	draft07Sec  = "https://json-schema.org/draft-07/schema#"
+	draft202012 = "https://json-schema.org/draft/2020-12/schema"
+)
+
+// isValidSchemaVersion checks if the given schema version is supported
+func isValidSchemaVersion(version string) bool {
+	return version == "" || version == draft07 || version == draft07Sec || version == draft202012
+}
+
+// isDraft07 checks if the schema version is draft-07
+func isDraft07(version string) bool {
+	return version == draft07 || version == draft07Sec
+}
+
+// isDraft202012 checks if the schema version is draft 2020-12
+func isDraft202012(version string) bool {
+	return version == "" || version == draft202012 // empty defaults to 2020-12
+}
 
 // Validate validates the instance, which must be a JSON value, against the schema.
 // It returns nil if validation is successful or an error if it is not.
 // If the schema type is "object", instance can be a map[string]any or a struct.
 func (rs *Resolved) Validate(instance any) error {
-	if s := rs.root.Schema; s != "" && s != draft202012 {
-		return fmt.Errorf("cannot validate version %s, only %s", s, draft202012)
+	if s := rs.root.Schema; !isValidSchemaVersion(s) {
+		return fmt.Errorf("cannot validate version %s, supported versions: draft-07 and draft 2020-12", s)
 	}
 	st := &state{rs: rs}
 	return st.validate(reflect.ValueOf(instance), st.rs.root, nil)
@@ -40,8 +59,8 @@ func (rs *Resolved) Validate(instance any) error {
 // TODO(jba): account for dynamic refs. This algorithm simple-mindedly
 // treats each schema with a default as its own root.
 func (rs *Resolved) validateDefaults() error {
-	if s := rs.root.Schema; s != "" && s != draft202012 {
-		return fmt.Errorf("cannot validate version %s, only %s", s, draft202012)
+	if s := rs.root.Schema; !isValidSchemaVersion(s) {
+		return fmt.Errorf("cannot validate version %s, supported versions: draft-07 and draft 2020-12", s)
 	}
 	st := &state{rs: rs}
 	for s := range rs.root.all() {
@@ -298,6 +317,8 @@ func (st *state) validate(instance reflect.Value, schema *Schema, callerAnns *an
 	// arrays
 	// TODO(jba): consider arrays of structs.
 	if instance.Kind() == reflect.Array || instance.Kind() == reflect.Slice {
+		// Handle both draft-07 and draft 2020-12 array validation using the same logic
+		// Draft-07 items arrays are converted to prefixItems during unmarshaling
 		// https://json-schema.org/draft/2020-12/json-schema-core#section-10.3.1
 		// This validate call doesn't collect annotations for the items of the instance; they are separate
 		// instances in their own right.
@@ -312,6 +333,8 @@ func (st *state) validate(instance reflect.Value, schema *Schema, callerAnns *an
 		}
 		anns.noteEndIndex(min(len(schema.PrefixItems), instance.Len()))
 
+		// For draft 2020-12: items applies to remaining items after prefixItems
+		// For draft-07: additionalItems applies to remaining items after items array
 		if schema.Items != nil {
 			for i := len(schema.PrefixItems); i < instance.Len(); i++ {
 				if err := st.validate(instance.Index(i), schema.Items, nil); err != nil {
@@ -320,6 +343,14 @@ func (st *state) validate(instance reflect.Value, schema *Schema, callerAnns *an
 			}
 			// Note that all the items in this array have been validated.
 			anns.allItems = true
+		} else if schema.AdditionalItems != nil {
+			// Draft-07 style: use additionalItems for remaining items
+			for i := len(schema.PrefixItems); i < instance.Len(); i++ {
+				if err := st.validate(instance.Index(i), schema.AdditionalItems, nil); err != nil {
+					return err
+				}
+			}
+			anns.allItems = true
 		}
 
 		nContains := 0
@@ -524,6 +555,43 @@ func (st *state) validate(instance reflect.Value, schema *Schema, callerAnns *an
 				}
 			}
 		}
+
+		// Draft-07 dependencies (combines both property and schema dependencies)
+		if schema.Dependencies != nil {
+			for dprop, dep := range schema.Dependencies {
+				if hasProperty(dprop) {
+					switch v := dep.(type) {
+					case []interface{}:
+						// Array of strings - property dependencies
+						var reqs []string
+						for _, item := range v {
+							if str, ok := item.(string); ok {
+								reqs = append(reqs, str)
+							}
+						}
+						if m := missingProperties(reqs); len(m) > 0 {
+							return fmt.Errorf("dependencies[%q]: missing properties %q", dprop, m)
+						}
+					case map[string]interface{}:
+						// Schema object - schema dependencies
+						// Convert map to Schema and resolve it properly
+						if data, err := json.Marshal(v); err == nil {
+							var depSchema Schema
+							if err := json.Unmarshal(data, &depSchema); err == nil {
+								// Resolve the dependency schema
+								resolved, err := depSchema.Resolve(nil)
+								if err != nil {
+									return fmt.Errorf("dependencies[%q]: failed to resolve schema: %w", dprop, err)
+								}
+								if err := resolved.Validate(instance.Interface()); err != nil {
+									return fmt.Errorf("dependencies[%q]: %w", dprop, err)
+								}
+							}
+						}
+					}
+				}
+			}
+		}
 		if schema.UnevaluatedProperties != nil && !anns.allProperties {
 			// This looks a lot like AdditionalProperties, but depends on in-place keywords like allOf
 			// in addition to sibling keywords.