feat: Add automatic function description generation for AI function callbacks

- Generate descriptions from function/method names when none provided
- Add warning logs recommending explicit description setting
- Add integration tests for auto-generated descriptions

Author: tzolov

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/client/AnthropicChatClientIT.java

@@ -42,6 +42,7 @@
 import org.springframework.ai.chat.model.ChatResponse;
 import org.springframework.ai.converter.BeanOutputConverter;
 import org.springframework.ai.converter.ListOutputConverter;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.test.context.SpringBootTest;
@@ -221,6 +222,25 @@ void functionCallTest() {
 		assertThat(response).contains("30", "10", "15");
 	}
 
+	@Test
+	void functionCallWithGeneratedDescription() {
+
+		// @formatter:off
+		String response = ChatClient.create(this.chatModel).prompt()
+				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
+				.functions(FunctionCallback.builder()
+					.function("getCurrentWeatherInLocation", new MockWeatherService())
+					.inputType(MockWeatherService.Request.class)
+					.build())
+				.call()
+				.content();
+		// @formatter:on
+
+		logger.info("Response: {}", response);
+
+		assertThat(response).contains("30", "10", "15");
+	}
+
 	@Test
 	void defaultFunctionCallTest() {
 

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/client/AnthropicChatClientMethodFunctionCallbackIT.java

@@ -51,6 +51,25 @@ void beforeEach() {
 		arguments.clear();
 	}
 
+	@Test
+	void methodGetWeatherGeneratedDescription() {
+
+		// @formatter:off
+		String response = ChatClient.create(this.chatModel).prompt()
+				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
+				.functions(FunctionCallback.builder()
+					.method("getWeatherInLocation", String.class, Unit.class)
+					.targetClass(TestFunctionClass.class)
+					.build())
+				.call()
+				.content();
+		// @formatter:on
+
+		logger.info("Response: {}", response);
+
+		assertThat(response).contains("30", "10", "15");
+	}
+
 	@Test
 	void methodGetWeatherStatic() {
 
@@ -201,6 +220,10 @@ public static void argumentLessReturnVoid() {
 			arguments.put("method called", "argumentLessReturnVoid");
 		}
 
+		public static String getWeatherInLocation(String city, Unit unit) {
+			return getWeatherStatic(city, unit);
+		}
+
 		public static String getWeatherStatic(String city, Unit unit) {
 
 			logger.info("City: " + city + " Unit: " + unit);

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

@@ -23,6 +23,8 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.json.JsonMapper;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import org.springframework.ai.chat.model.ToolContext;
 import org.springframework.ai.model.ModelOptionsUtils;
@@ -31,9 +33,11 @@
 import org.springframework.ai.model.function.FunctionCallback.MethodInvokerBuilder;
 import org.springframework.ai.model.function.FunctionCallbackContext.SchemaType;
 import org.springframework.ai.util.JacksonUtils;
+import org.springframework.ai.util.ParsingUtils;
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
+import org.springframework.util.StringUtils;
 
 /**
  * @author Christian Tzolov
@@ -42,6 +46,8 @@
 
 public class DefaultFunctionCallbackBuilder implements FunctionCallback.Builder {
 
+	private final static Logger logger = LoggerFactory.getLogger(DefaultFunctionCallbackBuilder.class);
+
 	private String description;
 
 	private SchemaType schemaType = SchemaType.JSON_SCHEMA;
@@ -151,7 +157,6 @@ public FunctionInvokerBuilder<I, O> inputType(ParameterizedTypeReference<?> inpu
 		@Override
 		public FunctionCallback build() {
 
-			Assert.hasText(description, "Description must not be empty");
 			Assert.notNull(objectMapper, "ObjectMapper must not be null");
 			Assert.hasText(this.name, "Name must not be empty");
 			Assert.notNull(responseConverter, "ResponseConverter must not be null");
@@ -165,10 +170,17 @@ public FunctionCallback build() {
 			BiFunction<I, ToolContext, O> finalBiFunction = (this.biFunction != null) ? this.biFunction
 					: (request, context) -> this.function.apply(request);
 
-			return new FunctionCallbackWrapper(this.name, description, inputTypeSchema, this.inputType,
+			return new FunctionCallbackWrapper(this.name, this.getDescription(), inputTypeSchema, this.inputType,
 					(Function<I, String>) responseConverter, objectMapper, finalBiFunction);
 		}
 
+		private String getDescription() {
+			if (StringUtils.hasText(description)) {
+				return description;
+			}
+			return generateDescription(this.name);
+		}
+
 	}
 
 	public class MethodInvokerBuilderImpl implements FunctionCallback.MethodInvokerBuilder {
@@ -215,10 +227,29 @@ public FunctionCallback build() {
 			Assert.isTrue(this.targetClass != null || this.targetObject != null,
 					"Target class or object must not be null");
 			var method = ReflectionUtils.findMethod(targetClass, methodName, argumentTypes);
-			return new MethodFunctionCallback(this.targetObject, method, description, objectMapper, this.name,
+			return new MethodFunctionCallback(this.targetObject, method, this.getDescription(), objectMapper, this.name,
 					responseConverter);
 		}
 
+		private String getDescription() {
+			if (StringUtils.hasText(description)) {
+				return description;
+			}
+
+			return generateDescription(StringUtils.hasText(this.name) ? this.name : this.methodName);
+		}
+
+	}
+
+	private String generateDescription(String fromName) {
+
+		String generatedDescription = ParsingUtils.reConcatenateCamelCase(fromName, " ");
+
+		logger.warn("Description is not set! A best effort attempt to generate a description:'{}' from the:'{}'",
+				generatedDescription, fromName);
+		logger.warn("It is recommended to set the Description explicitly! Use the 'description()' method!");
+
+		return generatedDescription;
 	}
 
 }

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

@@ -122,7 +122,7 @@ public class MethodFunctionCallback implements FunctionCallback {
 
 		this.inputSchema = this.generateJsonSchema(methodParameters);
 
-		logger.info("Generated JSON Schema: {}", this.inputSchema);
+		logger.debug("Generated JSON Schema: {}", this.inputSchema);
 	}
 
 	@Override