[FEATURE] avoid second round trip for function call

models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatClient.java

@@ -20,6 +20,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.stream.Collectors;
@@ -48,6 +49,7 @@
 import org.springframework.ai.chat.prompt.Prompt;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractFunctionCallSupport;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.ai.model.function.FunctionCallbackContext;
 import org.springframework.ai.retry.RetryUtils;
 import org.springframework.http.ResponseEntity;
@@ -391,6 +393,16 @@ public ChatCompletion build() {
 
 	}
 
+	@Override
+	protected boolean hasReturningFunction(RequestMessage responseMessage) {
+		return responseMessage.content()
+			.stream()
+			.filter(c -> c.type() == MediaContent.Type.TOOL_USE)
+			.map(MediaContent::name)
+			.map(functionName -> Optional.ofNullable(this.functionCallbackRegister.get(functionName)))
+			.anyMatch(functionCallback -> functionCallback.map(FunctionCallback::returningFunction).orElse(false));
+	}
+
 	@Override
 	protected ChatCompletionRequest doCreateToolResponseRequest(ChatCompletionRequest previousRequest,
 			RequestMessage responseMessage, List<RequestMessage> conversationHistory) {
@@ -414,8 +426,9 @@ protected ChatCompletionRequest doCreateToolResponseRequest(ChatCompletionReques
 
 			String functionResponse = this.functionCallbackRegister.get(functionName)
 				.call(ModelOptionsUtils.toJsonString(functionArguments));
-
-			toolResults.add(new MediaContent(Type.TOOL_RESULT, functionCallId, functionResponse));
+			if (functionResponse != null) {
+				toolResults.add(new MediaContent(Type.TOOL_RESULT, functionCallId, functionResponse));
+			}
 		}
 
 		// Add the function response to the conversation.

models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/AzureOpenAiChatClient.java

@@ -28,6 +28,7 @@
 import com.azure.ai.openai.models.ChatRequestSystemMessage;
 import com.azure.ai.openai.models.ChatRequestToolMessage;
 import com.azure.ai.openai.models.ChatRequestUserMessage;
+import com.azure.ai.openai.models.ChatResponseMessage;
 import com.azure.ai.openai.models.CompletionsFinishReason;
 import com.azure.ai.openai.models.ContentFilterResultsForPrompt;
 import com.azure.ai.openai.models.FunctionCall;
@@ -50,6 +51,7 @@
 import org.springframework.ai.chat.prompt.Prompt;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractFunctionCallSupport;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.ai.model.function.FunctionCallbackContext;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
@@ -513,6 +515,15 @@ private ChatCompletionsOptions copy(ChatCompletionsOptions fromOptions) {
 		return copyOptions;
 	}
 
+	@Override
+	protected boolean hasReturningFunction(ChatRequestMessage responseMessage) {
+		return ((ChatRequestAssistantMessage) responseMessage).getToolCalls()
+			.stream()
+			.map(toolCall -> ((ChatCompletionsFunctionToolCall) toolCall).getFunction().getName())
+			.map(functionName -> Optional.ofNullable(this.functionCallbackRegister.get(functionName)))
+			.anyMatch(functionCallback -> functionCallback.map(FunctionCallback::returningFunction).orElse(false));
+	}
+
 	@Override
 	protected ChatCompletionsOptions doCreateToolResponseRequest(ChatCompletionsOptions previousRequest,
 			ChatRequestMessage responseMessage, List<ChatRequestMessage> conversationHistory) {
@@ -530,8 +541,10 @@ protected ChatCompletionsOptions doCreateToolResponseRequest(ChatCompletionsOpti
 
 			String functionResponse = this.functionCallbackRegister.get(functionName).call(functionArguments);
 
-			// Add the function response to the conversation.
-			conversationHistory.add(new ChatRequestToolMessage(functionResponse, toolCall.getId()));
+			if (functionResponse != null) {
+				// Add the function response to the conversation.
+				conversationHistory.add(new ChatRequestToolMessage(functionResponse, toolCall.getId()));
+			}
 		}
 
 		// Recursively call chatCompletionWithTools until the model doesn't call a

models/spring-ai-azure-openai/src/test/java/org/springframework/ai/azure/openai/function/AzureOpenAiChatClientFunctionCallIT.java

@@ -118,6 +118,29 @@ void streamFunctionCallTest() {
 		assertThat(content).containsAnyOf("15.0", "15");
 	}
 
+	@Test
+	void functionCallWithoutCompleteRoundTrip() {
+
+		UserMessage userMessage = new UserMessage("What's the weather like in San Francisco?");
+
+		List<Message> messages = new ArrayList<>(List.of(userMessage));
+
+		final var spyingMockWeatherService = new SpyingMockWeatherService();
+		var promptOptions = AzureOpenAiChatOptions.builder()
+			.withDeploymentName(selectedModel)
+			.withFunctionCallbacks(List.of(FunctionCallbackWrapper.builder(spyingMockWeatherService)
+				.withName("getCurrentWeather")
+				.withDescription("Get the current weather in a given location")
+				.build()))
+			.build();
+
+		ChatResponse response = chatClient.call(new Prompt(messages, promptOptions));
+
+		logger.info("Response: {}", response);
+		final var interceptedRequest = spyingMockWeatherService.getInterceptedRequest();
+		assertThat(interceptedRequest.location()).containsIgnoringCase("San Francisco");
+	}
+
 	@SpringBootConfiguration
 	public static class TestConfiguration {
 

models/spring-ai-azure-openai/src/test/java/org/springframework/ai/azure/openai/function/SpyingMockWeatherService.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2023 - 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.ai.azure.openai.function;
+
+import java.util.function.Function;
+
+public class SpyingMockWeatherService implements Function<MockWeatherService.Request, Void> {
+
+	private MockWeatherService.Request interceptedRequest = null;
+
+	@Override
+	public Void apply(MockWeatherService.Request request) {
+		interceptedRequest = request;
+		return null;
+	}
+
+	public MockWeatherService.Request getInterceptedRequest() {
+		return interceptedRequest;
+	}
+
+}

models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/MistralAiChatClient.java

@@ -33,6 +33,7 @@
 import org.springframework.ai.mistralai.api.MistralAiApi.ChatCompletionRequest;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractFunctionCallSupport;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.ai.model.function.FunctionCallbackContext;
 import org.springframework.ai.retry.RetryUtils;
 import org.springframework.http.ResponseEntity;
@@ -98,7 +99,6 @@ public ChatResponse call(Prompt prompt) {
 		var request = createRequest(prompt, false);
 
 		return retryTemplate.execute(ctx -> {
-
 			ResponseEntity<ChatCompletion> completionEntity = this.callWithFunctionSupport(request);
 
 			var chatCompletion = completionEntity.getBody();
@@ -239,13 +239,18 @@ private List<MistralAiApi.FunctionTool> getFunctionTools(Set<String> functionNam
 		}).toList();
 	}
 
-	//
-	// Function Calling Support
-	//
+	@Override
+	protected boolean hasReturningFunction(ChatCompletionMessage responseMessage) {
+		return responseMessage.toolCalls()
+			.stream()
+			.map(toolCall -> toolCall.function().name())
+			.map(functionName -> Optional.ofNullable(this.functionCallbackRegister.get(functionName)))
+			.anyMatch(functionCallback -> functionCallback.map(FunctionCallback::returningFunction).orElse(false));
+	}
+
 	@Override
 	protected ChatCompletionRequest doCreateToolResponseRequest(ChatCompletionRequest previousRequest,
 			ChatCompletionMessage responseMessage, List<ChatCompletionMessage> conversationHistory) {
-
 		// Every tool-call item requires a separate function call and a response (TOOL)
 		// message.
 		for (ToolCall toolCall : responseMessage.toolCalls()) {
@@ -258,10 +263,12 @@ protected ChatCompletionRequest doCreateToolResponseRequest(ChatCompletionReques
 			}
 
 			String functionResponse = this.functionCallbackRegister.get(functionName).call(functionArguments);
+			if (functionResponse != null) {
+				// Add the function response to the conversation.
+				conversationHistory.add(new ChatCompletionMessage(functionResponse, ChatCompletionMessage.Role.TOOL,
+						functionName, null));
+			}
 
-			// Add the function response to the conversation.
-			conversationHistory
-				.add(new ChatCompletionMessage(functionResponse, ChatCompletionMessage.Role.TOOL, functionName, null));
 		}
 
 		// Recursively call chatCompletionWithTools until the model doesn't call a

models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatClient.java

@@ -27,6 +27,7 @@
 import org.springframework.ai.chat.prompt.Prompt;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractFunctionCallSupport;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.ai.model.function.FunctionCallbackContext;
 import org.springframework.ai.openai.api.OpenAiApi;
 import org.springframework.ai.openai.api.OpenAiApi.ChatCompletion;
@@ -324,6 +325,15 @@ private List<OpenAiApi.FunctionTool> getFunctionTools(Set<String> functionNames)
 		}).toList();
 	}
 
+	@Override
+	protected boolean hasReturningFunction(ChatCompletionMessage responseMessage) {
+		return responseMessage.toolCalls()
+			.stream()
+			.map(toolCall -> toolCall.function().name())
+			.map(functionName -> Optional.ofNullable(this.functionCallbackRegister.get(functionName)))
+			.anyMatch(functionCallback -> functionCallback.map(FunctionCallback::returningFunction).orElse(false));
+	}
+
 	@Override
 	protected ChatCompletionRequest doCreateToolResponseRequest(ChatCompletionRequest previousRequest,
 			ChatCompletionMessage responseMessage, List<ChatCompletionMessage> conversationHistory) {
@@ -340,10 +350,11 @@ protected ChatCompletionRequest doCreateToolResponseRequest(ChatCompletionReques
 			}
 
 			String functionResponse = this.functionCallbackRegister.get(functionName).call(functionArguments);
-
-			// Add the function response to the conversation.
-			conversationHistory
-				.add(new ChatCompletionMessage(functionResponse, Role.TOOL, functionName, toolCall.id(), null));
+			if (functionResponse != null) {
+				// Add the function response to the conversation.
+				conversationHistory
+					.add(new ChatCompletionMessage(functionResponse, Role.TOOL, functionName, toolCall.id(), null));
+			}
 		}
 
 		// Recursively call chatCompletionWithTools until the model doesn't call a

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

@@ -44,6 +44,7 @@
 import org.springframework.ai.chat.prompt.Prompt;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractFunctionCallSupport;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.ai.model.function.FunctionCallbackContext;
 import org.springframework.ai.vertexai.gemini.metadata.VertexAiChatResponseMetadata;
 import org.springframework.ai.vertexai.gemini.metadata.VertexAiUsage;
@@ -57,6 +58,7 @@
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -406,6 +408,14 @@ public void destroy() throws Exception {
 		}
 	}
 
+	@Override
+	protected boolean hasReturningFunction(Content responseMessage) {
+		final var functionName = responseMessage.getPartsList().get(0).getFunctionCall().getName();
+		return Optional.ofNullable(this.functionCallbackRegister.get(functionName))
+			.map(FunctionCallback::returningFunction)
+			.orElse(false);
+	}
+
 	@Override
 	protected GeminiRequest doCreateToolResponseRequest(GeminiRequest previousRequest, Content responseMessage,
 			List<Content> conversationHistory) {
@@ -420,17 +430,18 @@ protected GeminiRequest doCreateToolResponseRequest(GeminiRequest previousReques
 		}
 
 		String functionResponse = this.functionCallbackRegister.get(functionName).call(functionArguments);
-
-		Content contentFnResp = Content.newBuilder()
-			.addParts(Part.newBuilder()
-				.setFunctionResponse(FunctionResponse.newBuilder()
-					.setName(functionCall.getName())
-					.setResponse(jsonToStruct(functionResponse))
+		if (functionResponse != null) {
+			Content contentFnResp = Content.newBuilder()
+				.addParts(Part.newBuilder()
+					.setFunctionResponse(FunctionResponse.newBuilder()
+						.setName(functionCall.getName())
+						.setResponse(jsonToStruct(functionResponse))
+						.build())
 					.build())
-				.build())
-			.build();
+				.build();
 
-		conversationHistory.add(contentFnResp);
+			conversationHistory.add(contentFnResp);
+		}
 
 		return new GeminiRequest(conversationHistory, previousRequest.model());
 	}

spring-ai-core/src/main/java/org/springframework/ai/model/function/AbstractFunctionCallSupport.java

@@ -60,20 +60,17 @@ protected Set<String> handleFunctionCallbackConfigurations(FunctionCallingOption
 
 		if (options != null) {
 			if (!CollectionUtils.isEmpty(options.getFunctionCallbacks())) {
-				options.getFunctionCallbacks().stream().forEach(functionCallback -> {
-
+				options.getFunctionCallbacks().forEach(functionCallback -> {
 					// Register the tool callback.
 					if (isRuntimeCall) {
 						this.functionCallbackRegister.put(functionCallback.getName(), functionCallback);
+						// Automatically enable the function, usually from prompt
+						// callback.
+						functionToCall.add(functionCallback.getName());
 					}
 					else {
 						this.functionCallbackRegister.putIfAbsent(functionCallback.getName(), functionCallback);
 					}
-
-					// Automatically enable the function, usually from prompt callback.
-					if (isRuntimeCall) {
-						functionToCall.add(functionCallback.getName());
-					}
 				});
 			}
 
@@ -147,6 +144,9 @@ protected Resp handleFunctionCallOrReturn(Req request, Resp response) {
 
 		Req newRequest = this.doCreateToolResponseRequest(request, responseMessage, conversationHistory);
 
+		if (!this.hasReturningFunction(responseMessage)) {
+			return response;
+		}
 		return this.callWithFunctionSupport(newRequest);
 	}
 
@@ -180,6 +180,8 @@ protected Flux<Resp> handleFunctionCallOrReturnStream(Req request, Flux<Resp> re
 
 	}
 
+	abstract protected boolean hasReturningFunction(Msg responseMessage);
+
 	abstract protected Req doCreateToolResponseRequest(Req previousRequest, Msg responseMessage,
 			List<Msg> conversationHistory);