🐛 Vertex API admit only one tool per request, but tools can have multiple function inside

Author: Grogdunn

models/spring-ai-vertex-ai-gemini/src/main/java/org/springframework/ai/vertexai/gemini/VertexAiGeminiChatClient.java

@@ -349,16 +349,19 @@ else if (message instanceof AssistantMessage assistantMessage) {
 
 	private List<Tool> getFunctionTools(Set<String> functionNames) {
 
-		return this.resolveFunctionCallbacks(functionNames).stream().map(functionCallback -> {
-			FunctionDeclaration functionDeclaration = FunctionDeclaration.newBuilder()
+		final var tool = Tool.newBuilder();
+
+		final var functionDeclarations = this.resolveFunctionCallbacks(functionNames)
+			.stream()
+			.map(functionCallback -> FunctionDeclaration.newBuilder()
 				.setName(functionCallback.getName())
 				.setDescription(functionCallback.getDescription())
 				.setParameters(jsonToSchema(functionCallback.getInputTypeSchema()))
 				// .setParameters(toOpenApiSchema(functionCallback.getInputTypeSchema()))
-				.build();
-
-			return Tool.newBuilder().addFunctionDeclarations(functionDeclaration).build();
-		}).toList();
+				.build())
+			.toList();
+		tool.addAllFunctionDeclarations(functionDeclarations);
+		return List.of(tool.build());
 	}
 
 	private static String structToJson(Struct struct) {

models/spring-ai-vertex-ai-gemini/src/test/java/org/springframework/ai/vertexai/gemini/function/VertexAiGeminiChatClientFunctionCallingIT.java

@@ -15,19 +15,13 @@
  */
 package org.springframework.ai.vertexai.gemini.function;
 
-import java.util.ArrayList;
-import java.util.List;
-import java.util.stream.Collectors;
-
 import com.google.cloud.vertexai.Transport;
 import com.google.cloud.vertexai.VertexAI;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import reactor.core.publisher.Flux;
-
 import org.springframework.ai.chat.ChatResponse;
 import org.springframework.ai.chat.Generation;
 import org.springframework.ai.chat.messages.AssistantMessage;
@@ -42,8 +36,15 @@
 import org.springframework.boot.SpringBootConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.context.annotation.Bean;
+import reactor.core.publisher.Flux;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 
 @SpringBootTest
 @EnabledIfEnvironmentVariable(named = "VERTEX_AI_GEMINI_PROJECT_ID", matches = ".*")
@@ -178,6 +179,48 @@ public void functionCallTestInferredOpenApiSchemaStream() {
 
 	}
 
+	//Gemini wants single tool with multiple function, instead multiple tools with single function
+	@Test
+	public void canDeclareMultipleFunctions() {
+
+		UserMessage userMessage = new UserMessage(
+				"What's the weather like in San Francisco, in Paris and in Tokyo, Japan? Use Multi-turn function calling. Provide answer for all requested locations.");
+
+		List<Message> messages = new ArrayList<>(List.of(userMessage));
+
+		final var weatherFunction = FunctionCallbackWrapper.builder(new MockWeatherService())
+			.withSchemaType(SchemaType.OPEN_API_SCHEMA)
+			.withName("getCurrentWeather")
+			.withDescription("Get the current weather in a given location")
+			.build();
+		final var theAnswer = FunctionCallbackWrapper.builder(new TheAnswerMock())
+			.withSchemaType(SchemaType.OPEN_API_SCHEMA)
+			.withName("theAnswerToTheUniverse")
+			.withDescription("the answer to the ultimate question of life, the universe, and everything")
+			.build();
+		var promptOptions = VertexAiGeminiChatOptions.builder()
+			.withModel(VertexAiGeminiChatClient.ChatModel.GEMINI_PRO.getValue())
+			.withFunctionCallbacks(List.of(weatherFunction, theAnswer))
+			.build();
+
+		ChatResponse response = vertexGeminiClient.call(new Prompt(messages, promptOptions));
+
+		String responseString = response.getResult().getOutput().getContent();
+
+		logger.info("Response: {}", responseString);
+		assertNotNull(responseString);
+
+	}
+
+	public static class TheAnswerMock implements Function<String, Integer> {
+
+		@Override
+		public Integer apply(String s) {
+			return 42;
+		}
+
+	}
+
 	@SpringBootConfiguration
 	public static class TestConfiguration {