Add validation for prompt name uniqueness across the service.

- **New `PromptUniquenessValidator`**: Detects duplicate prompt names within services
- **Updated examples**: Updated the examples to use the new naming convention.
- **Only Service and Operations support**: Since we are not able to parse the prompts at resource level in the MCP Server, updated the trait selector to allow only service or operation level definition.

Prevents runtime conflicts when services define prompts with the same name at different levels (e.g., service vs operation). This supports the established naming convention of `serviceName__prompt-name-as-defined-in-trait` which provides namespace disambiguation and aligns with MCP specification requirements.

Author: yasmewad

examples/mcp-server/src/main/resources/software/amazon/smithy/java/example/server/mcp/main.smithy

@@ -19,7 +19,7 @@ use smithy.ai#prompts
         arguments: GetCodingStatisticsInput
         preferWhen: "User wants to analyze developer productivity, review coding activity, or understand technology usage patterns"
     }
-    employee_lookup: {
+    Test_employee: {
         description: "General employee lookup and information retrieval service"
         template: "This service provides employee information including personal details and coding statistics. Use get_employee_info for basic details or get_coding_stats for development metrics."
         preferWhen: "User needs any employee-related information or wants to understand available employee data"

mcp/mcp-server/src/main/java/software/amazon/smithy/java/mcp/server/McpServer.java

@@ -5,6 +5,8 @@
 
 package software.amazon.smithy.java.mcp.server;
 
+import static software.amazon.smithy.java.mcp.server.PromptLoader.normalize;
+
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.PrintWriter;
@@ -146,7 +148,7 @@ private void handleRequest(JsonRpcRequest req) {
                     var promptName = req.getParams().getMember("name").asString();
                     var promptArguments = req.getParams().getMember("arguments");
 
-                    var prompt = prompts.get(promptName);
+                    var prompt = prompts.get(normalize(promptName));
 
                     if (prompt == null) {
                         internalError(req, new RuntimeException("Prompt not found: " + promptName));

mcp/mcp-server/src/main/java/software/amazon/smithy/java/mcp/server/PromptLoader.java

@@ -54,7 +54,7 @@ public static Map<String, Prompt> loadPrompts(Collection<Service> services) {
 
             });
             for (Map.Entry<String, PromptTemplateDefinition> entry : promptDefinitions.entrySet()) {
-                var promptName = entry.getKey().toLowerCase();
+                var promptName = entry.getKey();
                 var promptTemplateDefinition = entry.getValue();
                 var templateString = promptTemplateDefinition.getTemplate();
 
@@ -76,8 +76,20 @@ public static Map<String, Prompt> loadPrompts(Collection<Service> services) {
                                 : List.of())
                         .build();
 
+                var normalizedName = normalize(promptName);
+
+                if (prompts.containsKey(normalizedName)) {
+                    var existingPrompt = prompts.get(normalizedName);
+                    throw new RuntimeException(String.format(
+                            "Duplicate normalized prompt name '%s' found. " +
+                                    "Original name '%s' conflicts with previously registered name '%s'.",
+                            normalizedName,
+                            promptName,
+                            existingPrompt.promptInfo().getName()));
+                }
+
                 prompts.put(
-                        promptName,
+                        normalizedName,
                         new Prompt(promptInfo, finalTemplateString));
             }
         }
@@ -118,4 +130,8 @@ public static List<PromptArgument> convertArgumentShapeToPromptArgument(Schema a
 
         return promptArguments;
     }
+
+    public static String normalize(String promptName) {
+        return promptName.toLowerCase();
+    }
 }

mcp/mcp-server/src/test/java/software/amazon/smithy/java/mcp/server/McpServerTest.java

@@ -395,6 +395,18 @@ void testPromptsList() {
         assertEquals("search_users", servicePromptMap.get("name").asString());
         assertEquals("Test Template", servicePromptMap.get("description").asString());
         assertTrue(servicePromptMap.get("arguments").asList().isEmpty());
+
+        // Verify that all prompt names are normalized to lowercase
+        var promptNames = prompts.stream()
+                .map(p -> p.asStringMap().get("name").asString())
+                .toList();
+        assertTrue(promptNames.contains("search_users"));
+        assertTrue(promptNames.contains("perform_operation"));
+
+        // Verify all names are lowercase (normalized)
+        for (String name : promptNames) {
+            assertEquals(name.toLowerCase(), name, "Prompt name should be normalized to lowercase: " + name);
+        }
     }
 
     @Test
@@ -430,6 +442,76 @@ void testPromptsGetWithValidPrompt() {
         assertEquals("Search for if many results expected.", content.get("text").asString());
     }
 
+    @Test
+    void testPromptsGetWithDifferentCasing() {
+        server = McpServer.builder()
+                .input(input)
+                .output(output)
+                .addService("test-mcp",
+                        ProxyService.builder()
+                                .service(ShapeId.from("smithy.test#TestService"))
+                                .proxyEndpoint("http://localhost")
+                                .model(MODEL)
+                                .build())
+                .build();
+
+        server.start();
+
+        // Test with uppercase prompt name
+        write("prompts/get",
+                Document.of(Map.of(
+                        "name",
+                        Document.of("SEARCH_USERS"))));
+        var response = read();
+        var result = response.getResult().asStringMap();
+
+        assertEquals("Test Template", result.get("description").asString());
+        var messages = result.get("messages").asList();
+        assertEquals(1, messages.size());
+
+        var message = messages.get(0).asStringMap();
+        assertEquals("user", message.get("role").asString());
+        var content = message.get("content").asStringMap();
+        assertEquals("text", content.get("type").asString());
+        assertEquals("Search for if many results expected.", content.get("text").asString());
+
+        // Test with mixed case prompt name
+        write("prompts/get",
+                Document.of(Map.of(
+                        "name",
+                        Document.of("Search_Users"))));
+        response = read();
+        result = response.getResult().asStringMap();
+
+        assertEquals("Test Template", result.get("description").asString());
+        messages = result.get("messages").asList();
+        assertEquals(1, messages.size());
+
+        message = messages.get(0).asStringMap();
+        assertEquals("user", message.get("role").asString());
+        content = message.get("content").asStringMap();
+        assertEquals("text", content.get("type").asString());
+        assertEquals("Search for if many results expected.", content.get("text").asString());
+
+        // Test with perform_operation prompt in different case
+        write("prompts/get",
+                Document.of(Map.of(
+                        "name",
+                        Document.of("PERFORM_OPERATION"))));
+        response = read();
+        result = response.getResult().asStringMap();
+
+        assertEquals("perform operation", result.get("description").asString());
+        messages = result.get("messages").asList();
+        assertEquals(1, messages.size());
+
+        message = messages.get(0).asStringMap();
+        assertEquals("user", message.get("role").asString());
+        content = message.get("content").asStringMap();
+        assertEquals("text", content.get("type").asString());
+        assertEquals("use tool TestOperation with some information.", content.get("text").asString());
+    }
+
     @Test
     void testPromptsGetWithInvalidPrompt() {
         server = McpServer.builder()
@@ -452,6 +534,15 @@ void testPromptsGetWithInvalidPrompt() {
         var response = read();
         assertNotNull(response.getError());
         assertTrue(response.getError().getMessage().contains("Prompt not found: nonexistent_prompt"));
+
+        // Test with invalid prompt in different case - should still fail
+        write("prompts/get",
+                Document.of(Map.of(
+                        "name",
+                        Document.of("NONEXISTENT_PROMPT"))));
+        response = read();
+        assertNotNull(response.getError());
+        assertTrue(response.getError().getMessage().contains("Prompt not found: NONEXISTENT_PROMPT"));
     }
 
     @Test