diff --git a/lib/src/core/definitions/data_schema.dart b/lib/src/core/definitions/data_schema.dart
index 22731bff..af27337f 100644
--- a/lib/src/core/definitions/data_schema.dart
+++ b/lib/src/core/definitions/data_schema.dart
@@ -61,7 +61,8 @@ class DataSchema {
     Set<String>? parsedFields,
   ]) {
     parsedFields = parsedFields ?? {};
-    final atType = json.parseArrayField<String>("@type", parsedFields);
+    final atType =
+        json.parseArrayField<String>("@type", parsedFields: parsedFields);
     final title = json.parseField<String>("title", parsedFields);
     final titles = json.parseMapField<String>("titles", parsedFields);
     final description = json.parseField<String>("description", parsedFields);
@@ -69,7 +70,11 @@ class DataSchema {
         json.parseMapField<String>("descriptions", parsedFields);
     final constant = json.parseField<Object>("constant", parsedFields);
     final defaultValue = json.parseField<Object>("default", parsedFields);
-    final enumeration = json.parseField<List<Object?>>("enum", parsedFields);
+    final enumeration = json.parseArrayField<Object?>(
+      "enum",
+      parsedFields: parsedFields,
+      minimalSize: 1,
+    );
     final readOnly = json.parseField<bool>("readOnly", parsedFields);
     final writeOnly = json.parseField<bool>("writeOnly", parsedFields);
     final format = json.parseField<String>("format", parsedFields);
diff --git a/lib/src/core/definitions/extensions/json_parser.dart b/lib/src/core/definitions/extensions/json_parser.dart
index cb9e38ca..4222cd19 100644
--- a/lib/src/core/definitions/extensions/json_parser.dart
+++ b/lib/src/core/definitions/extensions/json_parser.dart
@@ -90,8 +90,16 @@ extension ParseField on Map<String, dynamic> {
   ///
   /// If a [Set] of [parsedFields] is passed to this function, the field [name]
   /// will added. This can be used for filtering when parsing additional fields.
-  List<Uri>? parseUriArrayField(String name, [Set<String>? parsedFields]) {
-    final fieldValue = parseArrayField<String>(name, parsedFields);
+  List<Uri>? parseUriArrayField(
+    String name, {
+    Set<String>? parsedFields,
+    int minimalSize = 0,
+  }) {
+    final fieldValue = parseArrayField<String>(
+      name,
+      parsedFields: parsedFields,
+      minimalSize: minimalSize,
+    );
 
     if (fieldValue == null) {
       return null;
@@ -182,30 +190,46 @@ extension ParseField on Map<String, dynamic> {
   /// will be added. This can be used for filtering when parsing additional
   /// fields.
   List<T>? parseArrayField<T>(
-    String name, [
+    String name, {
     Set<String>? parsedFields,
-  ]) {
+    int minimalSize = 0,
+  }) {
     final fieldValue = parseField(name, parsedFields);
 
     if (fieldValue == null) {
       return null;
     }
 
-    if (fieldValue is T) {
-      return [fieldValue];
-    } else if (fieldValue is List<T>) {
-      return fieldValue;
+    final List<T> result;
+
+    if (fieldValue is List<T>) {
+      result = fieldValue;
+    } else if (fieldValue is T) {
+      result = [fieldValue];
     } else if (fieldValue is List<dynamic>) {
       final filteredArray = fieldValue.whereType<T>().toList(growable: false);
 
       if (filteredArray.length == fieldValue.length) {
-        return filteredArray;
+        result = filteredArray;
+      } else {
+        throw FormatException(
+          "Expected $T or a List of $T, but found a List member with invalid "
+          "type",
+        );
       }
+    } else {
+      throw FormatException(
+        "Expected $T or a List of $T, got ${fieldValue.runtimeType}",
+      );
     }
 
-    throw FormatException(
-      "Expected $T or a List of $T, got ${fieldValue.runtimeType}",
-    );
+    if (result.length < minimalSize) {
+      throw const FormatException(
+        "Expected a non-empty array, but encountered an empty one.",
+      );
+    }
+
+    return result;
   }
 
   /// Parses a field with a given [name] that can contain either a single value
@@ -218,10 +242,15 @@ extension ParseField on Map<String, dynamic> {
   /// will be added. This can be used for filtering when parsing additional
   /// fields.
   List<T> parseRequiredArrayField<T>(
-    String name, [
+    String name, {
     Set<String>? parsedFields,
-  ]) {
-    final result = parseArrayField<T>(name, parsedFields);
+    int minimalSize = 0,
+  }) {
+    final result = parseArrayField<T>(
+      name,
+      parsedFields: parsedFields,
+      minimalSize: minimalSize,
+    );
 
     if (result == null) {
       throw FormatException("Missing required field $name");
@@ -313,12 +342,14 @@ extension ParseField on Map<String, dynamic> {
     PrefixMapping prefixMapping,
     Set<String>? parsedFields,
   ) {
-    final fieldValue =
-        parseField<List<Map<String, dynamic>>>("forms", parsedFields);
+    final fieldValue = parseArrayField<Map<String, dynamic>>(
+      "forms",
+      parsedFields: parsedFields,
+      minimalSize: 1,
+    );
 
     return fieldValue
-        ?.whereType<Map<String, dynamic>>()
-        .map(
+        ?.map(
           (e) => Form.fromJson(
             e,
             prefixMapping,
@@ -340,13 +371,13 @@ extension ParseField on Map<String, dynamic> {
       parsedFields,
     );
 
-    if (forms != null) {
-      return forms;
+    if (forms == null) {
+      throw const FormatException(
+        'Missing "forms" member in InteractionAffordance',
+      );
     }
 
-    throw const FormatException(
-      'Missing "forms" member in InteractionAffordance',
-    );
+    return forms;
   }
 
   /// Parses [Link]s contained in this JSON object.
@@ -502,9 +533,14 @@ extension ParseField on Map<String, dynamic> {
   /// Processes this JSON value and tries to generate a [List] of
   /// [OperationType]s from it.
   List<OperationType>? parseOperationTypes(
-    Set<String>? parsedFields,
-  ) {
-    final opArray = parseArrayField<String>("op", parsedFields);
+    Set<String>? parsedFields, {
+    int minimalSize = 0,
+  }) {
+    final opArray = parseArrayField<String>(
+      "op",
+      parsedFields: parsedFields,
+      minimalSize: minimalSize,
+    );
 
     return opArray?.map(OperationType.fromString).toList();
   }
@@ -532,11 +568,13 @@ extension ParseField on Map<String, dynamic> {
   List<AdditionalExpectedResponse>? parseAdditionalExpectedResponse(
     PrefixMapping prefixMapping,
     String formContentType,
-    Set<String>? parsedFields,
-  ) {
+    Set<String>? parsedFields, {
+    int minimalSize = 0,
+  }) {
     final fieldValue = parseArrayField<Map<String, dynamic>>(
       "additionalResponses",
-      parsedFields,
+      parsedFields: parsedFields,
+      minimalSize: minimalSize,
     );
 
     if (fieldValue == null) {
diff --git a/lib/src/core/definitions/form.dart b/lib/src/core/definitions/form.dart
index 137602f7..8df6818a 100644
--- a/lib/src/core/definitions/form.dart
+++ b/lib/src/core/definitions/form.dart
@@ -53,8 +53,13 @@ class Form {
     final contentCoding =
         json.parseField<String>("contentCoding", parsedFields);
 
-    final security = json.parseArrayField<String>("security", parsedFields);
-    final scopes = json.parseArrayField<String>("scopes", parsedFields);
+    final security = json.parseArrayField<String>(
+      "security",
+      parsedFields: parsedFields,
+      minimalSize: 1,
+    );
+    final scopes =
+        json.parseArrayField<String>("scopes", parsedFields: parsedFields);
     final response = json.parseExpectedResponse(prefixMapping, parsedFields);
 
     final additionalResponses = json.parseAdditionalExpectedResponse(
diff --git a/lib/src/core/definitions/link.dart b/lib/src/core/definitions/link.dart
index c12ade1c..3ea92c63 100644
--- a/lib/src/core/definitions/link.dart
+++ b/lib/src/core/definitions/link.dart
@@ -39,7 +39,8 @@ class Link {
     final rel = json.parseField<String>("rel", parsedFields);
     final anchor = json.parseUriField("anchor", parsedFields);
     final sizes = json.parseField<String>("sizes", parsedFields);
-    final hreflang = json.parseArrayField<String>("hreflang", parsedFields);
+    final hreflang =
+        json.parseArrayField<String>("hreflang", parsedFields: parsedFields);
     final additionalFields =
         json.parseAdditionalFields(prefixMapping, parsedFields);
 
diff --git a/lib/src/core/definitions/security/ace_security_scheme.dart b/lib/src/core/definitions/security/ace_security_scheme.dart
index 06c1fab2..a02aa249 100644
--- a/lib/src/core/definitions/security/ace_security_scheme.dart
+++ b/lib/src/core/definitions/security/ace_security_scheme.dart
@@ -43,7 +43,8 @@ final class AceSecurityScheme extends SecurityScheme {
     final as = json.parseField<String>("ace:as", parsedFields);
     final cnonce = json.parseField<bool>("ace:cnonce", parsedFields);
     final audience = json.parseField<String>("ace:audience", parsedFields);
-    final scopes = json.parseArrayField<String>("ace:scopes", parsedFields);
+    final scopes =
+        json.parseArrayField<String>("ace:scopes", parsedFields: parsedFields);
 
     final additionalFields =
         json.parseAdditionalFields(prefixMapping, parsedFields);
diff --git a/lib/src/core/definitions/security/combo_security_scheme.dart b/lib/src/core/definitions/security/combo_security_scheme.dart
index d0aec36d..8fac24c3 100644
--- a/lib/src/core/definitions/security/combo_security_scheme.dart
+++ b/lib/src/core/definitions/security/combo_security_scheme.dart
@@ -4,6 +4,7 @@
 //
 // SPDX-License-Identifier: BSD-3-Clause
 
+import "package:collection/collection.dart";
 import "package:curie/curie.dart";
 
 import "../extensions/json_parser.dart";
@@ -38,8 +39,26 @@ final class ComboSecurityScheme extends SecurityScheme {
     final jsonLdType = json.parseArrayField<String>("@type");
     final proxy = json.parseUriField("proxy", parsedFields);
 
-    final oneOf = json.parseArrayField<String>("oneOf", parsedFields);
-    final allOf = json.parseArrayField<String>("allOf", parsedFields);
+    final oneOf = json.parseArrayField<String>(
+      "oneOf",
+      parsedFields: parsedFields,
+      minimalSize: 2,
+    );
+    final allOf = json.parseArrayField<String>(
+      "allOf",
+      parsedFields: parsedFields,
+      minimalSize: 2,
+    );
+
+    final count =
+        [oneOf, allOf].whereNotNull().fold(0, (previous, _) => previous + 1);
+
+    if (count != 1) {
+      throw FormatException(
+        "Expected exactly one of allOf or oneOf to be "
+        "defined, but $count were given.",
+      );
+    }
 
     final additionalFields =
         json.parseAdditionalFields(prefixMapping, parsedFields);
diff --git a/lib/src/core/definitions/security/oauth2_security_scheme.dart b/lib/src/core/definitions/security/oauth2_security_scheme.dart
index fd827e38..657d55da 100644
--- a/lib/src/core/definitions/security/oauth2_security_scheme.dart
+++ b/lib/src/core/definitions/security/oauth2_security_scheme.dart
@@ -46,7 +46,8 @@ final class OAuth2SecurityScheme extends SecurityScheme {
         json.parseField<String>("authorization", parsedFields);
     final token = json.parseField<String>("token", parsedFields);
     final refresh = json.parseField<String>("refresh", parsedFields);
-    final scopes = json.parseArrayField<String>("scopes", parsedFields);
+    final scopes =
+        json.parseArrayField<String>("scopes", parsedFields: parsedFields);
     final flow = json.parseRequiredField<String>("flow", parsedFields);
 
     final additionalFields =
diff --git a/lib/src/core/definitions/thing_description.dart b/lib/src/core/definitions/thing_description.dart
index 620601ed..1ba82fbc 100644
--- a/lib/src/core/definitions/thing_description.dart
+++ b/lib/src/core/definitions/thing_description.dart
@@ -58,7 +58,8 @@ class ThingDescription {
     final context = json.parseContext(parsedFields);
     final prefixMapping = context.prefixMapping;
 
-    final atType = json.parseArrayField<String>("@type", parsedFields);
+    final atType =
+        json.parseArrayField<String>("@type", parsedFields: parsedFields);
     final title = json.parseRequiredField<String>("title", parsedFields);
     final titles = json.parseMapField<String>("titles", parsedFields);
     final description = json.parseField<String>("description", parsedFields);
@@ -71,13 +72,22 @@ class ThingDescription {
     final base = json.parseUriField("base", parsedFields);
     final id = json.parseField<String>("id", parsedFields);
 
-    final security =
-        json.parseRequiredArrayField<String>("security", parsedFields);
+    final security = json.parseRequiredArrayField<String>(
+      "security",
+      parsedFields: parsedFields,
+    );
 
     final securityDefinitions =
         json.parseSecurityDefinitions(prefixMapping, parsedFields) ?? {};
 
     final forms = json.parseForms(prefixMapping, parsedFields);
+    // TODO: Move somewhere else
+    // TODO: Validate correct use of op-values
+    forms?.forEach((form) {
+      if (form.op == null) {
+        throw const FormatException('Missing "op" field in thing-level form.');
+      }
+    });
 
     final properties = json.parseProperties(prefixMapping, parsedFields);
     final actions = json.parseActions(prefixMapping, parsedFields);
@@ -85,7 +95,11 @@ class ThingDescription {
 
     final links = json.parseLinks(prefixMapping, parsedFields);
 
-    final profile = json.parseUriArrayField("profile", parsedFields);
+    final profile = json.parseUriArrayField(
+      "profile",
+      parsedFields: parsedFields,
+      minimalSize: 1,
+    );
     final schemaDefinitions = json.parseDataSchemaMapField(
       "schemaDefinitions",
       prefixMapping,
diff --git a/lib/src/core/definitions/thing_model.dart b/lib/src/core/definitions/thing_model.dart
index e7efa1c9..6dd576e9 100644
--- a/lib/src/core/definitions/thing_model.dart
+++ b/lib/src/core/definitions/thing_model.dart
@@ -8,7 +8,7 @@ import "extensions/json_parser.dart";
 
 /// Class representing a WoT Thing Model.
 ///
-/// See W3C WoT Thing Description Specificition, [section 10][spec link].
+/// See W3C WoT Thing Description Specification, [section 10][spec link].
 ///
 /// [spec link]: https://w3c.github.io/wot-thing-description/#thing-model
 class ThingModel {
diff --git a/test/core/definitions_test.dart b/test/core/definitions_test.dart
index 7e6f44b5..e1db1f00 100644
--- a/test/core/definitions_test.dart
+++ b/test/core/definitions_test.dart
@@ -638,30 +638,26 @@ void main() {
     );
   });
 
-  test(
-    "Should throw FormatExceptions for empty affordance forms in TDs",
-    () {
-      final invalidThingDescription = {
-        "@context": ["https://www.w3.org/2022/wot/td/v1.1"],
-        "title": "Thingweb WoT Thing",
-        "security": ["nosec_sc"],
-        "securityDefinitions": {
-          "nosec_sc": {
-            "scheme": "nosec",
-          },
+  test("Should throw FormatExceptions for empty affordance forms in TDs", () {
+    final invalidThingDescription = {
+      "@context": ["https://www.w3.org/2022/wot/td/v1.1"],
+      "title": "Thingweb WoT Thing",
+      "security": ["nosec_sc"],
+      "securityDefinitions": {
+        "nosec_sc": {
+          "scheme": "nosec",
         },
-        "actions": {
-          "testAction": {
-            "forms": [],
-          },
+      },
+      "actions": {
+        "testAction": {
+          "forms": [],
         },
-      };
+      },
+    };
 
-      expect(
-        () => ThingDescription.fromJson(invalidThingDescription),
-        throwsA(isA<FormatException>()),
-      );
-    },
-    skip: true,
-  );
+    expect(
+      () => ThingDescription.fromJson(invalidThingDescription),
+      throwsA(isA<FormatException>()),
+    );
+  });
 }