diff --git a/docs/spec/v2/metricset.json b/docs/spec/v2/metricset.json
index 9bfc90d1564..bbd73837086 100644
--- a/docs/spec/v2/metricset.json
+++ b/docs/spec/v2/metricset.json
@@ -8,6 +8,10 @@
       "additionalProperties": false,
       "patternProperties": {
         "^[^*\"]*$": {
+          "type": [
+            "null",
+            "object"
+          ],
           "properties": {
             "value": {
               "description": "Value holds the value of a single metric sample.",
diff --git a/model/modeldecoder/generator/jsonschema.go b/model/modeldecoder/generator/jsonschema.go
index 16f7ae7714f..65e25ea8aa2 100644
--- a/model/modeldecoder/generator/jsonschema.go
+++ b/model/modeldecoder/generator/jsonschema.go
@@ -121,10 +121,6 @@ func (g *JSONSchemaGenerator) generate(st structType, key string, prop *property
 		default:
 			switch t := f.Type().Underlying().(type) {
 			case *types.Map:
-				if _, ok := tags[tagPatternKeys]; !ok && name == "" {
-					// ignore the field in case no json name and no patternProperties are given
-					continue
-				}
 				nestedProp := property{Properties: make(map[string]*property)}
 				if err = generateJSONPropertyMap(&info, prop, &childProp, &nestedProp); err != nil {
 					break
@@ -240,7 +236,7 @@ type property struct {
 	Type        *propertyType `json:"type,omitempty"`
 	// AdditionalProperties should default to `true` and be set to `false`
 	// in case PatternProperties are set
-	AdditionalProperties *bool                `json:"additionalProperties,omitempty"`
+	AdditionalProperties interface{}          `json:"additionalProperties,omitempty"`
 	PatternProperties    map[string]*property `json:"patternProperties,omitempty"`
 	Properties           map[string]*property `json:"properties,omitempty"`
 	Items                *property            `json:"items,omitempty"`
diff --git a/model/modeldecoder/generator/map.go b/model/modeldecoder/generator/map.go
index ab417ed8709..40bc9616ef3 100644
--- a/model/modeldecoder/generator/map.go
+++ b/model/modeldecoder/generator/map.go
@@ -159,19 +159,23 @@ func generateJSONPropertyMap(info *fieldInfo, parent *property, child *property,
 	child.Type.add(TypeNameObject)
 	patternName, isPatternProp := info.tags[tagPatternKeys]
 	delete(info.tags, tagPatternKeys)
-	if !isPatternProp && name == "" {
-		// the object (map) can be places as a property with a defined key,
-		// or as a patternProperty with a defined key pattern
-		// if both are missing the field cannot be added
-		return fmt.Errorf("invalid combination: either json name or tag %s must be given", tagPatternKeys)
-	}
-	if !isPatternProp {
-		// if no pattern property is given, the child map will be nested directly as
-		// property inside the parent property, identified by it's json name
-		//   e.g. {"parent":{"properties":{"jsonNameXY":{..}}}}
+
+	nestedParent := child
+	if name == "" {
+		// The map does not have a json name defined, in which case it is nested directly
+		// inside the parent object's patternProperties/additionalProperties
+		//   e.g. {"parent":{"patternProperties":{"patternXY":{..}}}}
 		*nested = *child
-		parent.Properties[name] = nested
+		nestedParent = parent
+	} else {
+		// The map does have a json name defined, in which case it is nested as
+		// patternProperties/additionalProperties inside an object, which itself is nested
+		// inside the parent property, identified by its json name
+		//   e.g. {"parent":{"properties":{"jsonNameXY":{"patternProperties":{"patternXY":{..}}}}}}
+		parent.Properties[name] = child
 	}
+
+	haveValueSchema := len(info.tags) > 0
 	if maxLen, ok := info.tags[tagMaxLengthVals]; ok {
 		nested.MaxLength = json.Number(maxLen)
 		delete(info.tags, tagMaxLengthVals)
@@ -183,42 +187,30 @@ func generateJSONPropertyMap(info *fieldInfo, parent *property, child *property,
 		}
 		delete(info.tags, tagInputTypesVals)
 		nested.Type = &propertyType{names: names}
-	}
-	if !isPatternProp {
-		// nothing more to do when no key pattern is given
-		return nil
-	}
-	pattern, ok := info.parsed.patternVariables[patternName]
-	if !ok {
-		return fmt.Errorf("unhandled %s tag value %s", tagPatternKeys, pattern)
-	}
-	// for map key patterns two options are supported:
-	// - the map does not have a json name defined, in which case it is nested directly
-	//   inside the parent object's patternProperty
-	//   e.g. {"parent":{"patternProperties":{"patternXY":{..}}}}
-	// - the map does have a json name defined, in which case it is nested as
-	//   patternProperty inside an object, which itself is nested
-	//   inside the parent property, identified by it's json name
-	//   e.g. {"parent":{"properties":{"jsonNameXY":{"patternProperties":{"patternXY":{..}}}}}}
-	if name == "" {
-		if parent.PatternProperties == nil {
-			parent.PatternProperties = make(map[string]*property)
-		}
+	} else {
 		valueType := info.field.Type().Underlying().(*types.Map).Elem()
-		typeName, ok := propertyTypes[valueType.String()]
-		if !ok {
-			typeName = TypeNameObject
+		if !types.IsInterface(valueType) {
+			haveValueSchema = true
+			typeName, ok := propertyTypes[valueType.String()]
+			if !ok {
+				typeName = TypeNameObject
+			}
+			nested.Type = &propertyType{names: []propertyTypeName{typeName}}
 		}
-		nested.Type = &propertyType{names: []propertyTypeName{typeName}}
-		parent.PatternProperties[pattern] = nested
-		parent.AdditionalProperties = new(bool)
-		return nil
 	}
-	if child.PatternProperties == nil {
-		child.PatternProperties = make(map[string]*property)
+
+	if isPatternProp {
+		pattern, ok := info.parsed.patternVariables[patternName]
+		if !ok {
+			return fmt.Errorf("unhandled %s tag value %s", tagPatternKeys, pattern)
+		}
+		if nestedParent.PatternProperties == nil {
+			nestedParent.PatternProperties = make(map[string]*property)
+		}
+		nestedParent.PatternProperties[pattern] = nested
+		nestedParent.AdditionalProperties = false
+	} else if haveValueSchema {
+		nestedParent.AdditionalProperties = nested
 	}
-	child.PatternProperties[pattern] = nested
-	child.AdditionalProperties = new(bool)
-	parent.Properties[name] = child
 	return nil
 }