Detect duplicate prompt/tool names

deployment/src/main/java/io/quarkiverse/mcp/server/deployment/FeatureMethodBuildItem.java

@@ -1,5 +1,7 @@
 package io.quarkiverse.mcp.server.deployment;
 
+import java.util.Objects;
+
 import org.jboss.jandex.MethodInfo;
 
 import io.quarkus.arc.processor.BeanInfo;
@@ -17,12 +19,12 @@ final class FeatureMethodBuildItem extends MultiBuildItem {
 
     FeatureMethodBuildItem(BeanInfo bean, MethodInfo method, InvokerInfo invoker, String name, String description,
             Feature feature) {
-        this.bean = bean;
-        this.method = method;
-        this.invoker = invoker;
-        this.name = name;
+        this.bean = Objects.requireNonNull(bean);
+        this.method = Objects.requireNonNull(method);
+        this.invoker = Objects.requireNonNull(invoker);
+        this.name = Objects.requireNonNull(name);
         this.description = description;
-        this.feature = feature;
+        this.feature = Objects.requireNonNull(feature);
     }
 
     BeanInfo getBean() {
@@ -57,6 +59,12 @@ boolean isPrompt() {
         return feature == Feature.PROMPT;
     }
 
+    @Override
+    public String toString() {
+        return "FeatureMethodBuildItem [name=" + name + ", method=" + method.declaringClass() + "#" + method.name()
+                + "(), feature=" + feature + "]";
+    }
+
     enum Feature {
         PROMPT,
         TOOL

deployment/src/main/java/io/quarkiverse/mcp/server/deployment/McpServerProcessor.java

@@ -6,9 +6,13 @@
 
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import jakarta.enterprise.invoke.Invoker;
 import jakarta.inject.Singleton;
@@ -38,6 +42,7 @@
 import io.quarkus.arc.deployment.InvokerFactoryBuildItem;
 import io.quarkus.arc.deployment.SyntheticBeanBuildItem;
 import io.quarkus.arc.deployment.TransformedAnnotationsBuildItem;
+import io.quarkus.arc.deployment.ValidationPhaseBuildItem.ValidationErrorBuildItem;
 import io.quarkus.arc.processor.BeanInfo;
 import io.quarkus.arc.processor.BuiltinScope;
 import io.quarkus.arc.processor.InvokerBuilder;
@@ -106,7 +111,9 @@ void registerEndpoints(McpBuildTimeConfig config, HttpRootPathBuildItem rootPath
 
     @BuildStep
     void collectFeatureMethods(BeanDiscoveryFinishedBuildItem beanDiscovery, InvokerFactoryBuildItem invokerFactory,
-            BuildProducer<FeatureMethodBuildItem> features) {
+            BuildProducer<FeatureMethodBuildItem> features, BuildProducer<ValidationErrorBuildItem> errors) {
+        Map<Feature, List<FeatureMethodBuildItem>> found = new HashMap<>();
+
         for (BeanInfo bean : beanDiscovery.beanStream().classBeans().filter(this::hasFeatureMethod)) {
             ClassInfo beanClass = bean.getTarget().get().asClass();
             for (MethodInfo method : beanClass.methods()) {
@@ -123,8 +130,34 @@ void collectFeatureMethods(BeanDiscoveryFinishedBuildItem beanDiscovery, Invoker
                     String description = descValue != null ? descValue.asString() : "";
                     InvokerBuilder invokerBuilder = invokerFactory.createInvoker(bean, method)
                             .withInstanceLookup();
-                    features.produce(
-                            new FeatureMethodBuildItem(bean, method, invokerBuilder.build(), name, description, feature));
+                    FeatureMethodBuildItem fm = new FeatureMethodBuildItem(bean, method, invokerBuilder.build(), name,
+                            description, feature);
+                    features.produce(fm);
+                    found.compute(feature, (f, list) -> {
+                        if (list == null) {
+                            list = new ArrayList<>();
+                        }
+                        list.add(fm);
+                        return list;
+                    });
+                }
+            }
+        }
+
+        // Check duplicate names
+        for (List<FeatureMethodBuildItem> featureMethods : found.values()) {
+            Map<String, List<FeatureMethodBuildItem>> byName = featureMethods.stream()
+                    .collect(Collectors.toMap(FeatureMethodBuildItem::getName, List::of, (v1, v2) -> {
+                        List<FeatureMethodBuildItem> list = new ArrayList<>();
+                        list.addAll(v1);
+                        list.addAll(v2);
+                        return list;
+                    }));
+            for (List<FeatureMethodBuildItem> list : byName.values()) {
+                if (list.size() > 1) {
+                    String message = "Duplicate feature name found:\n\t%s"
+                            .formatted(list.stream().map(Object::toString).collect(Collectors.joining("\n\t")));
+                    errors.produce(new ValidationErrorBuildItem(new IllegalStateException(message)));
                 }
             }
         }

deployment/src/test/java/io/quarkiverse/mcp/server/test/validation/DuplicatePromptNameTest.java

@@ -0,0 +1,40 @@
+package io.quarkiverse.mcp.server.test.validation;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkiverse.mcp.server.Prompt;
+import io.quarkiverse.mcp.server.PromptResponse;
+import io.quarkus.test.QuarkusUnitTest;
+
+public class DuplicatePromptNameTest {
+
+    @RegisterExtension
+    public static final QuarkusUnitTest test = new QuarkusUnitTest()
+            .withApplicationRoot(root -> {
+                root.addClasses(InvalidPrompts.class);
+            })
+            .setExpectedException(IllegalStateException.class, true);
+
+    @Test
+    public void test() {
+        fail();
+    }
+
+    public static class InvalidPrompts {
+
+        @Prompt
+        PromptResponse foo() {
+            return null;
+        }
+
+        @Prompt(name = "foo")
+        PromptResponse foos() {
+            return null;
+        }
+
+    }
+
+}

deployment/src/test/java/io/quarkiverse/mcp/server/test/validation/DuplicateToolNameTest.java

@@ -0,0 +1,40 @@
+package io.quarkiverse.mcp.server.test.validation;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkiverse.mcp.server.Tool;
+import io.quarkiverse.mcp.server.ToolResponse;
+import io.quarkus.test.QuarkusUnitTest;
+
+public class DuplicateToolNameTest {
+
+    @RegisterExtension
+    public static final QuarkusUnitTest test = new QuarkusUnitTest()
+            .withApplicationRoot(root -> {
+                root.addClasses(InvalidTools.class);
+            })
+            .setExpectedException(IllegalStateException.class, true);
+
+    @Test
+    public void test() {
+        fail();
+    }
+
+    public static class InvalidTools {
+
+        @Tool
+        ToolResponse foo() {
+            return null;
+        }
+
+        @Tool(name = "foo")
+        ToolResponse foos() {
+            return null;
+        }
+
+    }
+
+}

runtime/src/main/java/io/quarkiverse/mcp/server/Prompt.java

@@ -13,8 +13,7 @@
  * Annotates a business method of a CDI bean as an exposed prompt template.
  * <p>
  * The result of a "prompt get" operation is always represented as a {@link PromptResponse}. However, the annotated method can
- * also return
- * other types that are converted according to the following rules.
+ * also return other types that are converted according to the following rules.
  * <ul>
  * <li>If the method returns a {@link PromptMessage} then the reponse has no description and contains the single
  * message object.</li>
@@ -45,12 +44,12 @@
     String ELEMENT_NAME = "<<element name>>";
 
     /**
-     *
+     * Each prompt must have a unique name. By default, the name is derived from the name of the annotated method.
      */
     String name() default ELEMENT_NAME;
 
     /**
-     *
+     * An optional description.
      */
     String description() default "";
 

runtime/src/main/java/io/quarkiverse/mcp/server/Tool.java

@@ -36,12 +36,12 @@
     String ELEMENT_NAME = "<<element name>>";
 
     /**
-     *
+     * Each tool must have a unique name. By default, the name is derived from the name of the annotated method.
      */
     String name() default ELEMENT_NAME;
 
     /**
-     *
+     * An optional description.
      */
     String description() default "";