public Builder clearFunctionDeclarations() {
      if (functionDeclarationsBuilder_ == null) {
        functionDeclarations_ = java.util.Collections.emptyList();
        bitField0_ = (bitField0_ & ~0x00000001);
        onChanged();
      } else {
        functionDeclarationsBuilder_.clear();
      }
      return this;
    }
<pre>
Optional. Function tool type.
One or more function declarations to be passed to the model along with the
current user query. Model may decide to call a subset of these functions
by populating [FunctionCall][google.cloud.aiplatform.v1.Part.function_call]
in the response. User should provide a
[FunctionResponse][google.cloud.aiplatform.v1.Part.function_response] for
each function call in the next turn. Based on the function responses, Model
will generate the final response back to the user. Maximum 128 function
declarations can be provided.
</pre>

<code>
repeated .google.cloud.vertexai.v1.FunctionDeclaration function_declarations = 1 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/Tool.java