Merge pull request #632 from modelcontextprotocol/ihrpr/resource-link

Add support for resource link

Author: ihrpr

README.md

@@ -192,8 +192,42 @@ server.registerTool(
     };
   }
 );
+
+// Tool that returns ResourceLinks
+server.registerTool(
+  "list-files",
+  {
+    title: "List Files",
+    description: "List project files",
+    inputSchema: { pattern: z.string() }
+  },
+  async ({ pattern }) => ({
+    content: [
+      { type: "text", text: `Found files matching "${pattern}":` },
+      // ResourceLinks let tools return references without file content
+      {
+        type: "resource_link",
+        uri: "file:///project/README.md",
+        name: "README.md",
+        mimeType: "text/markdown",
+        description: 'A README file'
+      },
+      {
+        type: "resource_link",
+        uri: "file:///project/src/index.ts",
+        name: "index.ts",
+        mimeType: "text/typescript",
+        description: 'An index file'
+      }
+    ]
+  })
+);
 ```
 
+#### ResourceLinks
+
+Tools can return `ResourceLink` objects to reference resources without embedding their full content. This is essential for performance when dealing with large files or many resources - clients can then selectively read only the resources they need using the provided URIs.
+
 ### Prompts
 
 Prompts are reusable templates that help LLMs interact with your server effectively:

src/examples/client/simpleStreamableHttp.ts

@@ -14,6 +14,9 @@ import {
   ListResourcesResultSchema,
   LoggingMessageNotificationSchema,
   ResourceListChangedNotificationSchema,
+  ReadResourceRequest,
+  ReadResourceResultSchema,
+  ResourceLink,
 } from '../../types.js';
 import { getDisplayName } from '../../shared/metadataUtils.js';
 
@@ -60,6 +63,7 @@ function printHelp(): void {
   console.log('  list-prompts               - List available prompts');
   console.log('  get-prompt [name] [args]   - Get a prompt with optional JSON arguments');
   console.log('  list-resources             - List available resources');
+  console.log('  read-resource <uri>        - Read a specific resource by URI');
   console.log('  help                       - Show this help');
   console.log('  quit                       - Exit the program');
 }
@@ -155,6 +159,14 @@ function commandLoop(): void {
           await listResources();
           break;
 
+        case 'read-resource':
+          if (args.length < 2) {
+            console.log('Usage: read-resource <uri>');
+          } else {
+            await readResource(args[1]);
+          }
+          break;
+
         case 'help':
           printHelp();
           break;
@@ -345,13 +357,37 @@ async function callTool(name: string, args: Record<string, unknown>): Promise<vo
     const result = await client.request(request, CallToolResultSchema);
 
     console.log('Tool result:');
+    const resourceLinks: ResourceLink[] = [];
+    
     result.content.forEach(item => {
       if (item.type === 'text') {
         console.log(`  ${item.text}`);
+      } else if (item.type === 'resource_link') {
+        const resourceLink = item as ResourceLink;
+        resourceLinks.push(resourceLink);
+        console.log(`  📁 Resource Link: ${resourceLink.name}`);
+        console.log(`     URI: ${resourceLink.uri}`);
+        if (resourceLink.mimeType) {
+          console.log(`     Type: ${resourceLink.mimeType}`);
+        }
+        if (resourceLink.description) {
+          console.log(`     Description: ${resourceLink.description}`);
+        }
+      } else if (item.type === 'resource') {
+        console.log(`  [Embedded Resource: ${item.resource.uri}]`);
+      } else if (item.type === 'image') {
+        console.log(`  [Image: ${item.mimeType}]`);
+      } else if (item.type === 'audio') {
+        console.log(`  [Audio: ${item.mimeType}]`);
       } else {
-        console.log(`  ${item.type} content:`, item);
+        console.log(`  [Unknown content type]:`, item);
       }
     });
+    
+    // Offer to read resource links
+    if (resourceLinks.length > 0) {
+      console.log(`\nFound ${resourceLinks.length} resource link(s). Use 'read-resource <uri>' to read their content.`);
+    }
   } catch (error) {
     console.log(`Error calling tool ${name}: ${error}`);
   }
@@ -489,6 +525,42 @@ async function listResources(): Promise<void> {
   }
 }
 
+async function readResource(uri: string): Promise<void> {
+  if (!client) {
+    console.log('Not connected to server.');
+    return;
+  }
+
+  try {
+    const request: ReadResourceRequest = {
+      method: 'resources/read',
+      params: { uri }
+    };
+
+    console.log(`Reading resource: ${uri}`);
+    const result = await client.request(request, ReadResourceResultSchema);
+
+    console.log('Resource contents:');
+    for (const content of result.contents) {
+      console.log(`  URI: ${content.uri}`);
+      if (content.mimeType) {
+        console.log(`  Type: ${content.mimeType}`);
+      }
+      
+      if ('text' in content && typeof content.text === 'string') {
+        console.log('  Content:');
+        console.log('  ---');
+        console.log(content.text.split('\n').map((line: string) => '  ' + line).join('\n'));
+        console.log('  ---');
+      } else if ('blob' in content && typeof content.blob === 'string') {
+        console.log(`  [Binary data: ${content.blob.length} bytes]`);
+      }
+    }
+  } catch (error) {
+    console.log(`Error reading resource ${uri}: ${error}`);
+  }
+}
+
 async function cleanup(): Promise<void> {
   if (client && transport) {
     try {

src/examples/server/simpleStreamableHttp.ts

@@ -5,7 +5,7 @@ import { McpServer } from '../../server/mcp.js';
 import { StreamableHTTPServerTransport } from '../../server/streamableHttp.js';
 import { getOAuthProtectedResourceMetadataUrl, mcpAuthMetadataRouter } from '../../server/auth/router.js';
 import { requireBearerAuth } from '../../server/auth/middleware/bearerAuth.js';
-import { CallToolResult, GetPromptResult, isInitializeRequest, ReadResourceResult } from '../../types.js';
+import { CallToolResult, GetPromptResult, isInitializeRequest, ReadResourceResult, ResourceLink } from '../../types.js';
 import { InMemoryEventStore } from '../shared/inMemoryEventStore.js';
 import { setupAuthServer } from './demoInMemoryOAuthProvider.js';
 import { OAuthMetadata } from 'src/shared/auth.js';
@@ -173,6 +173,99 @@ const getServer = () => {
       };
     }
   );
+
+  // Create additional resources for ResourceLink demonstration
+  server.registerResource(
+    'example-file-1',
+    'file:///example/file1.txt',
+    { 
+      title: 'Example File 1',
+      description: 'First example file for ResourceLink demonstration',
+      mimeType: 'text/plain' 
+    },
+    async (): Promise<ReadResourceResult> => {
+      return {
+        contents: [
+          {
+            uri: 'file:///example/file1.txt',
+            text: 'This is the content of file 1',
+          },
+        ],
+      };
+    }
+  );
+
+  server.registerResource(
+    'example-file-2',
+    'file:///example/file2.txt',
+    { 
+      title: 'Example File 2',
+      description: 'Second example file for ResourceLink demonstration',
+      mimeType: 'text/plain' 
+    },
+    async (): Promise<ReadResourceResult> => {
+      return {
+        contents: [
+          {
+            uri: 'file:///example/file2.txt',
+            text: 'This is the content of file 2',
+          },
+        ],
+      };
+    }
+  );
+
+  // Register a tool that returns ResourceLinks
+  server.registerTool(
+    'list-files',
+    {
+      title: 'List Files with ResourceLinks',
+      description: 'Returns a list of files as ResourceLinks without embedding their content',
+      inputSchema: {
+        includeDescriptions: z.boolean().optional().describe('Whether to include descriptions in the resource links'),
+      },
+    },
+    async ({ includeDescriptions = true }): Promise<CallToolResult> => {
+      const resourceLinks: ResourceLink[] = [
+        {
+          type: 'resource_link',
+          uri: 'https://example.com/greetings/default',
+          name: 'Default Greeting',
+          mimeType: 'text/plain',
+          ...(includeDescriptions && { description: 'A simple greeting resource' })
+        },
+        {
+          type: 'resource_link',
+          uri: 'file:///example/file1.txt',
+          name: 'Example File 1',
+          mimeType: 'text/plain',
+          ...(includeDescriptions && { description: 'First example file for ResourceLink demonstration' })
+        },
+        {
+          type: 'resource_link',
+          uri: 'file:///example/file2.txt',
+          name: 'Example File 2',
+          mimeType: 'text/plain',
+          ...(includeDescriptions && { description: 'Second example file for ResourceLink demonstration' })
+        }
+      ];
+
+      return {
+        content: [
+          {
+            type: 'text',
+            text: 'Here are the available files as resource links:',
+          },
+          ...resourceLinks,
+          {
+            type: 'text',
+            text: '\nYou can read any of these resources using their URI.',
+          }
+        ],
+      };
+    }
+  );
+
   return server;
 };