feat(tools): Add configurable exception handling for tool execution

Adds a new configuration property `spring.ai.tools.throw-exception-on-error` that controls how tool execution errors are handled:
- When false (default): errors are converted to messages and sent back to the AI model
- When true: errors are thrown as exceptions for the caller to handle

The implementation:
- Adds the property to ToolCallingProperties
- Updates ToolCallingAutoConfiguration to use the property
- Improves error handling in MCP tool callbacks to use ToolExecutionException
- Adds tests to verify both behaviors
- Updates documentation with the new property

Signed-off-by: Christian Tzolov <[email protected]>

Author: tzolov

auto-configurations/models/tool/spring-ai-autoconfigure-model-tool/src/main/java/org/springframework/ai/model/tool/autoconfigure/ToolCallingAutoConfiguration.java

@@ -77,8 +77,8 @@ ToolCallbackResolver toolCallbackResolver(GenericApplicationContext applicationC
 
 	@Bean
 	@ConditionalOnMissingBean
-	ToolExecutionExceptionProcessor toolExecutionExceptionProcessor() {
-		return new DefaultToolExecutionExceptionProcessor(false);
+	ToolExecutionExceptionProcessor toolExecutionExceptionProcessor(ToolCallingProperties properties) {
+		return new DefaultToolExecutionExceptionProcessor(properties.isThrowExceptionOnError());
 	}
 
 	@Bean

auto-configurations/models/tool/spring-ai-autoconfigure-model-tool/src/main/java/org/springframework/ai/model/tool/autoconfigure/ToolCallingProperties.java

@@ -31,6 +31,21 @@ public class ToolCallingProperties {
 
 	private final Observations observations = new Observations();
 
+	/**
+	 * If true, tool calling errors are thrown as exceptions for the caller to handle. If
+	 * false, errors are converted to messages and sent back to the AI model, allowing it
+	 * to process and respond to the error.
+	 */
+	private boolean throwExceptionOnError = false;
+
+	public boolean isThrowExceptionOnError() {
+		return this.throwExceptionOnError;
+	}
+
+	public void setThrowExceptionOnError(boolean throwExceptionOnError) {
+		this.throwExceptionOnError = throwExceptionOnError;
+	}
+
 	public static class Observations {
 
 		/**

auto-configurations/models/tool/spring-ai-autoconfigure-model-tool/src/test/java/org/springframework/ai/model/tool/autoconfigure/ToolCallingAutoConfigurationTests.java

@@ -26,7 +26,9 @@
 import org.springframework.ai.tool.ToolCallback;
 import org.springframework.ai.tool.ToolCallbackProvider;
 import org.springframework.ai.tool.annotation.Tool;
+import org.springframework.ai.tool.definition.ToolDefinition;
 import org.springframework.ai.tool.execution.DefaultToolExecutionExceptionProcessor;
+import org.springframework.ai.tool.execution.ToolExecutionException;
 import org.springframework.ai.tool.execution.ToolExecutionExceptionProcessor;
 import org.springframework.ai.tool.function.FunctionToolCallback;
 import org.springframework.ai.tool.method.MethodToolCallback;
@@ -127,6 +129,62 @@ void observationFilterEnabled() {
 			.run(context -> assertThat(context).hasSingleBean(ToolCallingContentObservationFilter.class));
 	}
 
+	@Test
+	void throwExceptionOnErrorDefault() {
+		new ApplicationContextRunner().withConfiguration(AutoConfigurations.of(ToolCallingAutoConfiguration.class))
+			.withUserConfiguration(Config.class)
+			.run(context -> {
+				var toolExecutionExceptionProcessor = context.getBean(ToolExecutionExceptionProcessor.class);
+				assertThat(toolExecutionExceptionProcessor).isInstanceOf(DefaultToolExecutionExceptionProcessor.class);
+
+				// Test behavior instead of accessing private field
+				// Create a mock tool definition and exception
+				var toolDefinition = ToolDefinition.builder()
+					.name("testTool")
+					.description("Test tool for exception handling")
+					.inputSchema("{\"type\":\"object\",\"properties\":{\"test\":{\"type\":\"string\"}}}")
+					.build();
+				var cause = new RuntimeException("Test error");
+				var exception = new ToolExecutionException(toolDefinition, cause);
+
+				// Default behavior should not throw exception
+				String result = toolExecutionExceptionProcessor.process(exception);
+				assertThat(result).isEqualTo("Test error");
+			});
+	}
+
+	@Test
+	void throwExceptionOnErrorEnabled() {
+		new ApplicationContextRunner().withConfiguration(AutoConfigurations.of(ToolCallingAutoConfiguration.class))
+			.withPropertyValues("spring.ai.tools.throw-exception-on-error=true")
+			.withUserConfiguration(Config.class)
+			.run(context -> {
+				var toolExecutionExceptionProcessor = context.getBean(ToolExecutionExceptionProcessor.class);
+				assertThat(toolExecutionExceptionProcessor).isInstanceOf(DefaultToolExecutionExceptionProcessor.class);
+
+				// Test behavior instead of accessing private field
+				// Create a mock tool definition and exception
+				var toolDefinition = ToolDefinition.builder()
+					.name("testTool")
+					.description("Test tool for exception handling")
+					.inputSchema("{\"type\":\"object\",\"properties\":{\"test\":{\"type\":\"string\"}}}")
+					.build();
+				var cause = new RuntimeException("Test error");
+				var exception = new ToolExecutionException(toolDefinition, cause);
+
+				// When property is set to true, it should throw the exception
+				assertThat(toolExecutionExceptionProcessor).extracting(processor -> {
+					try {
+						processor.process(exception);
+						return "No exception thrown";
+					}
+					catch (ToolExecutionException e) {
+						return "Exception thrown";
+					}
+				}).isEqualTo("Exception thrown");
+			});
+	}
+
 	static class WeatherService {
 
 		@Tool(description = "Get the weather in location. Return temperature in 36°F or 36°C format.")

mcp/common/src/main/java/org/springframework/ai/mcp/AsyncMcpToolCallback.java

@@ -27,6 +27,7 @@
 import org.springframework.ai.tool.ToolCallback;
 import org.springframework.ai.tool.definition.DefaultToolDefinition;
 import org.springframework.ai.tool.definition.ToolDefinition;
+import org.springframework.ai.tool.execution.ToolExecutionException;
 
 /**
  * Implementation of {@link ToolCallback} that adapts MCP tools to Spring AI's tool
@@ -41,7 +42,9 @@
  * <li>Manages JSON serialization/deserialization of tool inputs and outputs</li>
  * </ul>
  * <p>
- * Example usage: <pre>{@code
+ * Example usage:
+ *
+ * <pre>{@code
  * McpAsyncClient mcpClient = // obtain MCP client
  * Tool mcpTool = // obtain MCP tool definition
  * ToolCallback callback = new AsyncMcpToolCallback(mcpClient, mcpTool);
@@ -109,12 +112,19 @@ public String call(String functionInput) {
 		Map<String, Object> arguments = ModelOptionsUtils.jsonToMap(functionInput);
 		// Note that we use the original tool name here, not the adapted one from
 		// getToolDefinition
-		return this.asyncMcpClient.callTool(new CallToolRequest(this.tool.name(), arguments)).map(response -> {
-			if (response.isError() != null && response.isError()) {
-				throw new IllegalStateException("Error calling tool: " + response.content());
-			}
-			return ModelOptionsUtils.toJsonString(response.content());
-		}).block();
+		try {
+			return this.asyncMcpClient.callTool(new CallToolRequest(this.tool.name(), arguments)).map(response -> {
+				if (response.isError() != null && response.isError()) {
+					throw new ToolExecutionException(this.getToolDefinition(),
+							new IllegalStateException("Error calling tool: " + response.content()));
+				}
+				return ModelOptionsUtils.toJsonString(response.content());
+			}).block();
+		}
+		catch (Exception ex) {
+			throw new ToolExecutionException(this.getToolDefinition(), ex.getCause());
+		}
+
 	}
 
 	@Override

mcp/common/src/main/java/org/springframework/ai/mcp/SyncMcpToolCallback.java

@@ -16,18 +16,23 @@
 
 package org.springframework.ai.mcp;
 
+import java.lang.reflect.InvocationTargetException;
 import java.util.Map;
 
 import io.modelcontextprotocol.client.McpSyncClient;
 import io.modelcontextprotocol.spec.McpSchema.CallToolRequest;
 import io.modelcontextprotocol.spec.McpSchema.CallToolResult;
 import io.modelcontextprotocol.spec.McpSchema.Tool;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import org.springframework.ai.chat.model.ToolContext;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.tool.ToolCallback;
 import org.springframework.ai.tool.definition.DefaultToolDefinition;
 import org.springframework.ai.tool.definition.ToolDefinition;
+import org.springframework.ai.tool.execution.ToolExecutionException;
+import org.springframework.core.log.LogAccessor;
 
 /**
  * Implementation of {@link ToolCallback} that adapts MCP tools to Spring AI's tool
@@ -61,6 +66,8 @@
  */
 public class SyncMcpToolCallback implements ToolCallback {
 
+	private static final Logger logger = LoggerFactory.getLogger(SyncMcpToolCallback.class);
+
 	private final McpSyncClient mcpClient;
 
 	private final Tool tool;
@@ -113,11 +120,20 @@ public String call(String functionInput) {
 		Map<String, Object> arguments = ModelOptionsUtils.jsonToMap(functionInput);
 		// Note that we use the original tool name here, not the adapted one from
 		// getToolDefinition
-		CallToolResult response = this.mcpClient.callTool(new CallToolRequest(this.tool.name(), arguments));
-		if (response.isError() != null && response.isError()) {
-			throw new IllegalStateException("Error calling tool: " + response.content());
+		try {
+			CallToolResult response = this.mcpClient.callTool(new CallToolRequest(this.tool.name(), arguments));
+			if (response.isError() != null && response.isError()) {
+				logger.error("Error calling tool: {}", response.content());
+				throw new ToolExecutionException(this.getToolDefinition(),
+						new IllegalStateException("Error calling tool: " + response.content()));
+			}
+			return ModelOptionsUtils.toJsonString(response.content());
+		}
+		catch (Exception ex) {
+			logger.error("Exception while tool calling: ", ex);
+			throw new ToolExecutionException(this.getToolDefinition(), ex.getCause());
 		}
-		return ModelOptionsUtils.toJsonString(response.content());
+
 	}
 
 	@Override

spring-ai-docs/src/main/antora/modules/ROOT/pages/api/tools.adoc

@@ -1180,7 +1180,8 @@ ChatResponse newResponse = chatModel.call(new Prompt(chatMemory.get(conversation
 
 === Exception Handling
 
-When a tool call fails, the exception is propagated as a `ToolExecutionException` which can be caught to handle the error. A `ToolExecutionExceptionProcessor` can be used to handle a `ToolExecutionException` with two outcomes: either producing an error message to be sent back to the AI model or throwing an exception to be handled by the caller.
+When a tool call fails, the exception is propagated as a `ToolExecutionException` which can be caught to handle the error. 
+A `ToolExecutionExceptionProcessor` can be used to handle a `ToolExecutionException` with two outcomes: either producing an error message to be sent back to the AI model or throwing an exception to be handled by the caller.
 
 [source,java]
 ----
@@ -1198,6 +1199,16 @@ public interface ToolExecutionExceptionProcessor {
 
 If you're using any of the Spring AI Spring Boot Starters, `DefaultToolExecutionExceptionProcessor` is the autoconfigured implementation of the `ToolExecutionExceptionProcessor` interface. By default, the error message is sent back to the model. The `DefaultToolExecutionExceptionProcessor` constructor lets you set the `alwaysThrow` attribute to `true` or `false`. If `true`, an exception will be thrown instead of sending an error message back to the model.
 
+You can use the ``spring.ai.tools.throw-exception-on-error` property to control the behavior of the `DefaultToolExecutionExceptionProcessor` bean:
+
+[cols="6,3,1", stripes=even]
+|====
+| Property | Description | Default
+
+| `spring.ai.tools.throw-exception-on-error` | If `true`, tool calling errors are thrown as exceptions for the caller to handle. If `false`, errors are converted to messages and sent back to the AI model, allowing it to process and respond to the error.| `false`
+|====
+
+
 [source,java]
 ----
 @Bean