feat: add optional resource annotations

src/server/mcp.test.ts

@@ -2315,12 +2315,18 @@ describe.each(zodTestMatrix)('$zodVersionLabel', (entry: ZodMatrixEntry) => {
                 version: '1.0'
             });
 
+            const mockDate = new Date().toISOString();
             mcpServer.resource(
                 'test',
                 'test://resource',
                 {
                     description: 'Test resource',
-                    mimeType: 'text/plain'
+                    mimeType: 'text/plain',
+                    annotations: {
+                        audience: ['user'],
+                        priority: 0.5,
+                        lastModified: mockDate
+                    }
                 },
                 async () => ({
                     contents: [
@@ -2346,6 +2352,11 @@ describe.each(zodTestMatrix)('$zodVersionLabel', (entry: ZodMatrixEntry) => {
             expect(result.resources).toHaveLength(1);
             expect(result.resources[0].description).toBe('Test resource');
             expect(result.resources[0].mimeType).toBe('text/plain');
+            expect(result.resources[0].annotations).toEqual({
+                audience: ['user'],
+                priority: 0.5,
+                lastModified: mockDate
+            });
         });
 
         /***

src/shared/metadataUtils.ts

@@ -10,14 +10,14 @@ import { BaseMetadata } from '../types.js';
  * For other objects: title → name
  * This implements the spec requirement: "if no title is provided, name should be used for display purposes"
  */
-export function getDisplayName(metadata: BaseMetadata & { annotations?: { title?: string } }): string {
+export function getDisplayName(metadata: BaseMetadata | (BaseMetadata & { annotations?: { title?: string } })): string {
     // First check for title (not undefined and not empty string)
     if (metadata.title !== undefined && metadata.title !== '') {
         return metadata.title;
     }
 
     // Then check for annotations.title (only present in Tool objects)
-    if (metadata.annotations?.title) {
+    if ('annotations' in metadata && metadata.annotations?.title) {
         return metadata.annotations.title;
     }
 

src/spec.types.test.ts

@@ -656,6 +656,10 @@ const sdkTypeChecks = {
     ) => {
         sdk = spec;
         spec = sdk;
+    },
+    Annotations: (sdk: SDKTypes.Annotations, spec: SpecTypes.Annotations) => {
+        sdk = spec;
+        spec = sdk;
     }
 };
 
@@ -667,10 +671,7 @@ const MISSING_SDK_TYPES = [
     // These are inlined in the SDK:
     'Role',
     'Error', // The inner error object of a JSONRPCError
-    'URLElicitationRequiredError', // In the SDK, but with a custom definition
-    // These aren't supported by the SDK yet:
-    // TODO: Add definitions to the SDK
-    'Annotations'
+    'URLElicitationRequiredError' // In the SDK, but with a custom definition
 ];
 
 function extractExportedTypes(source: string): string[] {

src/types.test.ts

@@ -95,75 +95,130 @@ describe('Types', () => {
 
     describe('ContentBlock', () => {
         test('should validate text content', () => {
+            const mockDate = new Date().toISOString();
             const textContent = {
                 type: 'text',
-                text: 'Hello, world!'
+                text: 'Hello, world!',
+                annotations: {
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                }
             };
 
             const result = ContentBlockSchema.safeParse(textContent);
             expect(result.success).toBe(true);
             if (result.success) {
                 expect(result.data.type).toBe('text');
+                expect(result.data.annotations).toEqual({
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                });
             }
         });
 
         test('should validate image content', () => {
+            const mockDate = new Date().toISOString();
             const imageContent = {
                 type: 'image',
                 data: 'aGVsbG8=', // base64 encoded "hello"
-                mimeType: 'image/png'
+                mimeType: 'image/png',
+                annotations: {
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                }
             };
 
             const result = ContentBlockSchema.safeParse(imageContent);
             expect(result.success).toBe(true);
             if (result.success) {
                 expect(result.data.type).toBe('image');
+                expect(result.data.annotations).toEqual({
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                });
             }
         });
 
         test('should validate audio content', () => {
+            const mockDate = new Date().toISOString();
             const audioContent = {
                 type: 'audio',
                 data: 'aGVsbG8=', // base64 encoded "hello"
-                mimeType: 'audio/mp3'
+                mimeType: 'audio/mp3',
+                annotations: {
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                }
             };
 
             const result = ContentBlockSchema.safeParse(audioContent);
             expect(result.success).toBe(true);
             if (result.success) {
                 expect(result.data.type).toBe('audio');
+                expect(result.data.annotations).toEqual({
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                });
             }
         });
 
         test('should validate resource link content', () => {
+            const mockDate = new Date().toISOString();
             const resourceLink = {
                 type: 'resource_link',
                 uri: 'file:///path/to/file.txt',
                 name: 'file.txt',
-                mimeType: 'text/plain'
+                mimeType: 'text/plain',
+                annotations: {
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: new Date().toISOString()
+                }
             };
 
             const result = ContentBlockSchema.safeParse(resourceLink);
             expect(result.success).toBe(true);
             if (result.success) {
                 expect(result.data.type).toBe('resource_link');
+                expect(result.data.annotations).toEqual({
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                });
             }
         });
 
         test('should validate embedded resource content', () => {
+            const mockDate = new Date().toISOString();
             const embeddedResource = {
                 type: 'resource',
                 resource: {
                     uri: 'file:///path/to/file.txt',
                     mimeType: 'text/plain',
                     text: 'File contents'
+                },
+                annotations: {
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
                 }
             };
 
             const result = ContentBlockSchema.safeParse(embeddedResource);
             expect(result.success).toBe(true);
             if (result.success) {
                 expect(result.data.type).toBe('resource');
+                expect(result.data.annotations).toEqual({
+                    audience: ['user'],
+                    priority: 0.5,
+                    lastModified: mockDate
+                });
             }
         });
     });

src/types.ts

@@ -790,6 +790,26 @@ export const BlobResourceContentsSchema = ResourceContentsSchema.extend({
     blob: Base64Schema
 });
 
+/**
+ * Optional annotations providing clients additional context about a resource.
+ */
+export const AnnotationsSchema = z.object({
+    /**
+     * Intended audience(s) for the resource.
+     */
+    audience: z.array(z.enum(['user', 'assistant'])).optional(),
+
+    /**
+     * Importance hint for the resource, from 0 (least) to 1 (most).
+     */
+    priority: z.number().min(0).max(1).optional(),
+
+    /**
+     * ISO 8601 timestamp for the most recent modification.
+     */
+    lastModified: z.iso.datetime({ offset: true }).optional()
+});
+
 /**
  * A known resource that the server is capable of reading.
  */
@@ -813,6 +833,11 @@ export const ResourceSchema = z.object({
      */
     mimeType: z.optional(z.string()),
 
+    /**
+     * Optional annotations for the client.
+     */
+    annotations: AnnotationsSchema.optional(),
+
     /**
      * See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
      * for notes on _meta usage.
@@ -843,6 +868,11 @@ export const ResourceTemplateSchema = z.object({
      */
     mimeType: z.optional(z.string()),
 
+    /**
+     * Optional annotations for the client.
+     */
+    annotations: AnnotationsSchema.optional(),
+
     /**
      * See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
      * for notes on _meta usage.
@@ -1035,6 +1065,11 @@ export const TextContentSchema = z.object({
      */
     text: z.string(),
 
+    /**
+     * Optional annotations for the client.
+     */
+    annotations: AnnotationsSchema.optional(),
+
     /**
      * See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
      * for notes on _meta usage.
@@ -1056,6 +1091,11 @@ export const ImageContentSchema = z.object({
      */
     mimeType: z.string(),
 
+    /**
+     * Optional annotations for the client.
+     */
+    annotations: AnnotationsSchema.optional(),
+
     /**
      * See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
      * for notes on _meta usage.
@@ -1077,6 +1117,11 @@ export const AudioContentSchema = z.object({
      */
     mimeType: z.string(),
 
+    /**
+     * Optional annotations for the client.
+     */
+    annotations: AnnotationsSchema.optional(),
+
     /**
      * See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
      * for notes on _meta usage.
@@ -1120,6 +1165,10 @@ export const ToolUseContentSchema = z
 export const EmbeddedResourceSchema = z.object({
     type: z.literal('resource'),
     resource: z.union([TextResourceContentsSchema, BlobResourceContentsSchema]),
+    /**
+     * Optional annotations for the client.
+     */
+    annotations: AnnotationsSchema.optional(),
     /**
      * See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
      * for notes on _meta usage.
@@ -2219,6 +2268,7 @@ export type CancelledNotification = Infer<typeof CancelledNotificationSchema>;
 export type Icon = Infer<typeof IconSchema>;
 export type Icons = Infer<typeof IconsSchema>;
 export type BaseMetadata = Infer<typeof BaseMetadataSchema>;
+export type Annotations = Infer<typeof AnnotationsSchema>;
 
 /* Initialization */
 export type Implementation = Infer<typeof ImplementationSchema>;