Update vector-search.md

Added example and details to project the vector similarity score

Author: jcodella

articles/cosmos-db/mongodb/vcore/vector-search.md

@@ -122,11 +122,17 @@ To perform a vector search, use the `$search` aggregation pipeline stage in a Mo
         "vector": <vector_to_search>,
         "path": "<path_to_property>",
         "k": <num_results_to_return>
-      }
-    ...
+      },
+      "returnStoredSource": True }},
+  {
+    "$project": { "<custom_name_for_similarity_score>": {
+           "$meta": "searchScore" },
+            "document" : "$$ROOT"
+        }
   }
 }
 ```
+To retrieve the similarity score (`searchScore`) along with the documents found by the vector search, use the `$project` operator to include `searchScore` and rename it as `<custom_name_for_similarity_score>` in the results. Then the document is also projected as nested object. Note that the similarity score is calculated using the metric defined in the vector index.
 
 ### Query a vector index by using $search
 
@@ -142,8 +148,12 @@ db.exampleCollection.aggregate([
         "path": "vectorContent",
         "k": 2
       },
-    "returnStoredSource": true
-    }
+    "returnStoredSource": true }},
+  {
+    "$project": { "similarityScore": {
+           "$meta": "searchScore" },
+            "document" : "$$ROOT"
+        }
   }
 ]);
 ```
@@ -153,16 +163,22 @@ In this example, a vector search is performed by using `queryVector` as an input
 ```javascript
 [
   {
-    _id: ObjectId("645acb54413be5502badff94"),
-    name: 'Eugenia Lopez',
-    bio: 'Eugenia is the CEO of AdvenureWorks.',
-    vectorContent: [ 0.51, 0.12, 0.23 ]
+    similarityScore: 0.9465376,
+    document: {
+      _id: ObjectId("645acb54413be5502badff94"),
+      name: 'Eugenia Lopez',
+      bio: 'Eugenia is the CEO of AdvenureWorks.',
+      vectorContent: [ 0.51, 0.12, 0.23 ]
+    }
   },
   {
-    _id: ObjectId("645acb54413be5502badff97"),
-    name: 'Rory Nguyen',
-    bio: 'Rory Nguyen is the founder of AdventureWorks and the president of the Our Planet initiative.',
-    vectorContent: [ 0.91, 0.76, 0.83 ]
+    similarityScore: 0.9006955,
+    document: {
+      _id: ObjectId("645acb54413be5502badff97"),
+      name: 'Rory Nguyen',
+      bio: 'Rory Nguyen is the founder of AdventureWorks and the president of the Our Planet initiative.',
+      vectorContent: [ 0.91, 0.76, 0.83 ]
+    }
   }
 ]
 ```