diff --git a/src/metrics.ts b/src/metrics.ts
index 3acfbdf..aa8bc33 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -5,16 +5,16 @@ export enum MetricType {
   Gauge = 'gauge'
 }
 
-export type MetricMetadata = { [key: string]: any };
+export type MetricMetadata = Record<string, unknown>
 
-export function MetadataFromDocument(doc: AsyncAPIDocument, metadata: MetricMetadata = []): MetricMetadata {
-  metadata['_asyncapi_version'] = doc.version();
-  metadata['_asyncapi_servers'] = doc.allServers().all().length;
-  metadata['_asyncapi_channels'] = doc.allChannels().all().length;
-  metadata['_asyncapi_messages'] = doc.allMessages().all().length;
-  metadata['_asyncapi_operations_send'] = doc.allOperations().filterBySend().length;
-  metadata['_asyncapi_operations_receive'] = doc.allOperations().filterByReceive().length;
-  metadata['_asyncapi_schemas'] = doc.allSchemas().all().length;
+export function MetadataFromDocument(doc: AsyncAPIDocument, metadata: MetricMetadata = {}): MetricMetadata {
+  metadata['asyncapi_version'] = doc.version();
+  metadata['asyncapi_servers'] = doc.allServers().all().length;
+  metadata['asyncapi_channels'] = doc.allChannels().all().length;
+  metadata['asyncapi_messages'] = doc.allMessages().all().length;
+  metadata['asyncapi_operations_send'] = doc.allOperations().filterBySend().length;
+  metadata['asyncapi_operations_receive'] = doc.allOperations().filterByReceive().length;
+  metadata['asyncapi_schemas'] = doc.allSchemas().all().length;
   return metadata;
 }
   
diff --git a/test/metrics.spec.ts b/test/metrics.spec.ts
index 0168e7d..bd7b9bb 100644
--- a/test/metrics.spec.ts
+++ b/test/metrics.spec.ts
@@ -8,24 +8,24 @@ describe('Metrics', function() {
   it('MetadataFromDocument with no previous metadata', async function() {
     const {document} = await parser.parse(doc);
     const metadata = MetadataFromDocument(document as AsyncAPIDocument);
-    expect(metadata['_asyncapi_version']).toEqual('2.6.0');
-    expect(metadata['_asyncapi_servers']).toEqual(1);
-    expect(metadata['_asyncapi_channels']).toEqual(2);
-    expect(metadata['_asyncapi_messages']).toEqual(2);
-    expect(metadata['_asyncapi_operations_send']).toEqual(1);
-    expect(metadata['_asyncapi_operations_receive']).toEqual(1);
-    expect(metadata['_asyncapi_schemas']).toEqual(2);
+    expect(metadata['asyncapi_version']).toEqual('2.6.0');
+    expect(metadata['asyncapi_servers']).toEqual(1);
+    expect(metadata['asyncapi_channels']).toEqual(2);
+    expect(metadata['asyncapi_messages']).toEqual(2);
+    expect(metadata['asyncapi_operations_send']).toEqual(1);
+    expect(metadata['asyncapi_operations_receive']).toEqual(1);
+    expect(metadata['asyncapi_schemas']).toEqual(2);
   });
   it('MetadataFromDocument with previous metadata', async function() {
     const {document} = await parser.parse(doc);
     const metadata = MetadataFromDocument(document as AsyncAPIDocument, { test: true });
     expect(metadata['test']).toBeTruthy();
-    expect(metadata['_asyncapi_version']).toEqual('2.6.0');
-    expect(metadata['_asyncapi_servers']).toEqual(1);
-    expect(metadata['_asyncapi_channels']).toEqual(2);
-    expect(metadata['_asyncapi_messages']).toEqual(2);
-    expect(metadata['_asyncapi_operations_send']).toEqual(1);
-    expect(metadata['_asyncapi_operations_receive']).toEqual(1);
-    expect(metadata['_asyncapi_schemas']).toEqual(2);
+    expect(metadata['asyncapi_version']).toEqual('2.6.0');
+    expect(metadata['asyncapi_servers']).toEqual(1);
+    expect(metadata['asyncapi_channels']).toEqual(2);
+    expect(metadata['asyncapi_messages']).toEqual(2);
+    expect(metadata['asyncapi_operations_send']).toEqual(1);
+    expect(metadata['asyncapi_operations_receive']).toEqual(1);
+    expect(metadata['asyncapi_schemas']).toEqual(2);
   });
-});
\ No newline at end of file
+});