fix: return images as MCP image content type per spec

Images (PNG, JPG, GIF, WEBP, SVG) now returned as { type: 'image', data, mimeType }
per https://modelcontextprotocol.io/specification/2025-11-25/server/tools#image-content
Other binary files continue using embedded resource format { type: 'resource', ... }
Added audio content type to ToolOutput union for future use

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/tools/file-operations.ts

@@ -64,6 +64,10 @@ function getMimeType(filePath: string): string {
   return MIME_TYPES[ext] ?? 'application/octet-stream';
 }
 
+function isImageMimeType(mimeType: string): boolean {
+  return mimeType.startsWith('image/');
+}
+
 /**
  * Register all file operation tools
  */
@@ -175,7 +179,7 @@ export async function registerFileOperationTools(server: ObsidianMCPServer): Pro
   // T031: Read note tool
   server.registerTool(
     'obsidian_read_note',
-    'Read the content of a note from the Obsidian vault. Specify either the note name (file) or full path (path). For large files (e.g. PDFs), use max_chars and offset to read in chunks and avoid exceeding context limits. Binary files (ZIP, images, PDFs, etc.) are automatically detected and returned as an MCP embedded resource with a uri, mimeType, and base64-encoded blob field instead of plain text.',
+    'Read the content of a note from the Obsidian vault. Specify either the note name (file) or full path (path). For large files (e.g. PDFs), use max_chars and offset to read in chunks and avoid exceeding context limits. Binary files are automatically detected: images (PNG, JPG, GIF, WEBP, SVG) are returned as MCP image content (type: "image") with base64-encoded data and mimeType; all other binary files (ZIP, PDF, DOCX, etc.) are returned as MCP embedded resource content (type: "resource") with uri, mimeType, and base64-encoded blob.',
     {
       type: 'object',
       properties: {
@@ -198,7 +202,7 @@ export async function registerFileOperationTools(server: ObsidianMCPServer): Pro
       },
     },
     createToolHandler(
-      'Read the content of a note. Binary files are returned as an MCP embedded resource (type: "resource") with uri, mimeType, and a base64-encoded blob field.',
+      'Read the content of a note. Images (PNG, JPG, GIF, WEBP, SVG) are returned as MCP image content (type: "image") with base64-encoded data. Other binary files are returned as MCP embedded resource content (type: "resource") with uri, mimeType, and base64-encoded blob.',
       {
         type: 'object',
         properties: {
@@ -233,12 +237,28 @@ export async function registerFileOperationTools(server: ObsidianMCPServer): Pro
         const result = await executeObsidianCommandBinary('read', cmdArgs);
         handleCLIResult(result, { operation: 'read_note', identifier: sanitized.file || sanitized.path });
 
-        // Detect binary content from the raw buffer and return as MCP resource
+        // Detect binary content from the raw buffer and return as spec-appropriate MCP content
         if (result.stdoutBuffer && isBinaryContent(result.stdoutBuffer)) {
           const identifier = sanitized.file || sanitized.path as string;
+          const mimeType = getMimeType(identifier);
+          const base64 = result.stdoutBuffer.toString('base64');
+
+          // Images use the MCP image content type per spec
+          if (isImageMimeType(mimeType)) {
+            return {
+              content: [
+                {
+                  type: 'image' as const,
+                  data: base64,
+                  mimeType,
+                },
+              ],
+            };
+          }
+
+          // All other binary files use the embedded resource content type per spec
           const vaultName = process.env.OBSIDIAN_VAULT ?? 'vault';
           const uri = `obsidian://${encodeURIComponent(vaultName)}/${encodeURIComponent(identifier)}`;
-          const mimeType = getMimeType(identifier);
           return {
             content: [
               {
@@ -246,7 +266,7 @@ export async function registerFileOperationTools(server: ObsidianMCPServer): Pro
                 resource: {
                   uri,
                   mimeType,
-                  blob: result.stdoutBuffer.toString('base64'),
+                  blob: base64,
                 },
               },
             ],

src/utils/types.ts

@@ -18,6 +18,8 @@ export interface ToolInput {
 export interface ToolOutput {
   content: Array<
     | { type: 'text'; text: string }
+    | { type: 'image'; data: string; mimeType: string }
+    | { type: 'audio'; data: string; mimeType: string }
     | { type: 'resource'; resource: { uri: string; mimeType?: string; blob: string } }
   >;
   isError?: false;