feat: add a dynamic retrieval API

PiperOrigin-RevId: 681780557

google/cloud/aiplatform/v1/content.proto

@@ -560,6 +560,12 @@ message GroundingMetadata {
   // Optional. List of grounding support.
   repeated GroundingSupport grounding_supports = 6
       [(google.api.field_behavior) = OPTIONAL];
+
+  // Optional. Output only. Retrieval metadata.
+  optional RetrievalMetadata retrieval_metadata = 7 [
+    (google.api.field_behavior) = OPTIONAL,
+    (google.api.field_behavior) = OUTPUT_ONLY
+  ];
 }
 
 // Google search entry point.
@@ -572,3 +578,14 @@ message SearchEntryPoint {
   // url> tuple.
   bytes sdk_blob = 2 [(google.api.field_behavior) = OPTIONAL];
 }
+
+// Metadata related to retrieval in the grounding flow.
+message RetrievalMetadata {
+  // Optional. Score indicating how likely information from google search could
+  // help answer the prompt. The score is in the range `[0, 1]`, where 0 is the
+  // least likely and 1 is the most likely. This score is only populated when
+  // google search grounding and dynamic retrieval is enabled. It will be
+  // compared to the threshold to determine whether to trigger google search.
+  float google_search_dynamic_retrieval_score = 2
+      [(google.api.field_behavior) = OPTIONAL];
+}

google/cloud/aiplatform/v1/tool.proto

@@ -142,7 +142,29 @@ message VertexAISearch {
 }
 
 // Tool to retrieve public web data for grounding, powered by Google.
-message GoogleSearchRetrieval {}
+message GoogleSearchRetrieval {
+  // Specifies the dynamic retrieval configuration for the given source.
+  DynamicRetrievalConfig dynamic_retrieval_config = 2;
+}
+
+// Describes the options to customize dynamic retrieval.
+message DynamicRetrievalConfig {
+  // The mode of the predictor to be used in dynamic retrieval.
+  enum Mode {
+    // Always trigger retrieval.
+    MODE_UNSPECIFIED = 0;
+
+    // Run retrieval only when system decides it is necessary.
+    MODE_DYNAMIC = 1;
+  }
+
+  // The mode of the predictor to be used in dynamic retrieval.
+  Mode mode = 1;
+
+  // Optional. The threshold to be used in dynamic retrieval.
+  // If not set, a system default value is used.
+  optional float dynamic_threshold = 2 [(google.api.field_behavior) = OPTIONAL];
+}
 
 // Tool config. This config is shared for all tools provided in the request.
 message ToolConfig {