diff --git a/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java b/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java
index f970249ab7e..b5743d80bfd 100644
--- a/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java
+++ b/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java
@@ -34,6 +34,7 @@
 import org.springframework.ai.model.tool.ToolExecutionResult;
 import org.springframework.ai.tool.definition.ToolDefinition;
 import org.springframework.ai.util.json.JsonParser;
+import org.springframework.lang.Nullable;
 import reactor.core.publisher.Flux;
 
 import org.springframework.ai.chat.messages.AssistantMessage;
@@ -125,8 +126,9 @@ public class OllamaChatModel extends AbstractToolCallSupport implements ChatMode
 
 	@Deprecated
 	public OllamaChatModel(OllamaApi ollamaApi, OllamaOptions defaultOptions,
-			FunctionCallbackResolver functionCallbackResolver, List<FunctionCallback> toolFunctionCallbacks,
-			ObservationRegistry observationRegistry, ModelManagementOptions modelManagementOptions) {
+			@Nullable FunctionCallbackResolver functionCallbackResolver,
+			@Nullable List<FunctionCallback> toolFunctionCallbacks, ObservationRegistry observationRegistry,
+			ModelManagementOptions modelManagementOptions) {
 		super(functionCallbackResolver, defaultOptions, toolFunctionCallbacks);
 		Assert.notNull(ollamaApi, "ollamaApi must not be null");
 		Assert.notNull(defaultOptions, "defaultOptions must not be null");
diff --git a/models/spring-ai-ollama/src/test/java/org/springframework/ai/ollama/OllamaChatModelTests.java b/models/spring-ai-ollama/src/test/java/org/springframework/ai/ollama/OllamaChatModelTests.java
index f5ca4e68636..dc5b9bfb725 100644
--- a/models/spring-ai-ollama/src/test/java/org/springframework/ai/ollama/OllamaChatModelTests.java
+++ b/models/spring-ai-ollama/src/test/java/org/springframework/ai/ollama/OllamaChatModelTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 the original author or authors.
+ * Copyright 2023-2025 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.
@@ -20,6 +20,7 @@
 import java.time.Instant;
 import java.util.List;
 
+import io.micrometer.observation.ObservationRegistry;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
@@ -27,10 +28,13 @@
 
 import org.springframework.ai.chat.metadata.ChatResponseMetadata;
 import org.springframework.ai.chat.metadata.DefaultUsage;
+import org.springframework.ai.chat.model.ChatModel;
 import org.springframework.ai.chat.model.ChatResponse;
+import org.springframework.ai.model.tool.ToolCallingManager;
 import org.springframework.ai.ollama.api.OllamaApi;
 import org.springframework.ai.ollama.api.OllamaModel;
 import org.springframework.ai.ollama.api.OllamaOptions;
+import org.springframework.ai.ollama.management.ModelManagementOptions;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -40,16 +44,39 @@
  * @author Jihoon Kim
  * @author Christian Tzolov
  * @author Alexandros Pappas
+ * @author Thomas Vitale
  * @since 1.0.0
  */
 @ExtendWith(MockitoExtension.class)
-public class OllamaChatModelTests {
+class OllamaChatModelTests {
 
 	@Mock
 	OllamaApi ollamaApi;
 
 	@Test
-	public void buildOllamaChatModel() {
+	void buildOllamaChatModelWithDeprecatedConstructor() {
+		ChatModel chatModel = new OllamaChatModel(this.ollamaApi,
+				OllamaOptions.builder().model(OllamaModel.MISTRAL).build(), null, null, ObservationRegistry.NOOP,
+				ModelManagementOptions.builder().build());
+		assertThat(chatModel).isNotNull();
+	}
+
+	@Test
+	void buildOllamaChatModelWithConstructor() {
+		ChatModel chatModel = new OllamaChatModel(this.ollamaApi,
+				OllamaOptions.builder().model(OllamaModel.MISTRAL).build(), ToolCallingManager.builder().build(),
+				ObservationRegistry.NOOP, ModelManagementOptions.builder().build());
+		assertThat(chatModel).isNotNull();
+	}
+
+	@Test
+	void buildOllamaChatModelWithBuilder() {
+		ChatModel chatModel = OllamaChatModel.builder().ollamaApi(ollamaApi).build();
+		assertThat(chatModel).isNotNull();
+	}
+
+	@Test
+	void buildOllamaChatModel() {
 		Exception exception = assertThrows(IllegalArgumentException.class,
 				() -> OllamaChatModel.builder()
 					.ollamaApi(this.ollamaApi)
@@ -60,7 +87,7 @@ public void buildOllamaChatModel() {
 	}
 
 	@Test
-	public void buildChatResponseMetadata() {
+	void buildChatResponseMetadata() {
 
 		Long evalDuration = 1000L;
 		Integer evalCount = 101;
@@ -83,7 +110,7 @@ public void buildChatResponseMetadata() {
 	}
 
 	@Test
-	public void buildChatResponseMetadataAggregationWithNonEmptyMetadata() {
+	void buildChatResponseMetadataAggregationWithNonEmptyMetadata() {
 
 		Long evalDuration = 1000L;
 		Integer evalCount = 101;
diff --git a/spring-ai-core/src/main/java/org/springframework/ai/model/tool/LegacyToolCallingManager.java b/spring-ai-core/src/main/java/org/springframework/ai/model/tool/LegacyToolCallingManager.java
index f0356bcacfa..4176c6c7c22 100644
--- a/spring-ai-core/src/main/java/org/springframework/ai/model/tool/LegacyToolCallingManager.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/model/tool/LegacyToolCallingManager.java
@@ -55,6 +55,7 @@
 @Deprecated
 public class LegacyToolCallingManager implements ToolCallingManager {
 
+	@Nullable
 	private final FunctionCallbackResolver functionCallbackResolver;
 
 	private final Map<String, FunctionCallback> functionCallbacks = new HashMap<>();
@@ -64,11 +65,11 @@ public class LegacyToolCallingManager implements ToolCallingManager {
 		.build();
 
 	public LegacyToolCallingManager(@Nullable FunctionCallbackResolver functionCallbackResolver,
-			List<FunctionCallback> functionCallbacks) {
-		Assert.notNull(functionCallbacks, "functionCallbacks cannot be null");
-		Assert.noNullElements(functionCallbacks.toArray(), "functionCallbacks cannot contain null elements");
+			@Nullable List<FunctionCallback> functionCallbacks) {
 		this.functionCallbackResolver = functionCallbackResolver;
-		functionCallbacks.forEach(toolCallback -> this.functionCallbacks.put(toolCallback.getName(), toolCallback));
+		if (functionCallbacks != null) {
+			functionCallbacks.forEach(toolCallback -> this.functionCallbacks.put(toolCallback.getName(), toolCallback));
+		}
 	}
 
 	@Override