fix: simplify output schemas for text-only tools and add structuredContent

For text-only tool responses, simplify outputSchemas from complex nested
arrays to simple { content: z.string() } format. All tool responses now
include structuredContent matching their outputSchema, fixing MCP protocol
violations when tools had output schemas but no structured content.

This applies to both filesystem and everything servers.

Author: domdomegg

src/everything/everything.ts

@@ -547,21 +547,25 @@ export const createServer = () => {
 
     if (name === ToolName.ECHO) {
       const validatedArgs = EchoSchema.parse(args);
+      const text = `Echo: ${validatedArgs.message}`;
       return {
-        content: [{ type: "text", text: `Echo: ${validatedArgs.message}` }],
+        content: [{ type: "text", text }],
+        structuredContent: { content: text }
       };
     }
 
     if (name === ToolName.ADD) {
       const validatedArgs = AddSchema.parse(args);
       const sum = validatedArgs.a + validatedArgs.b;
+      const text = `The sum of ${validatedArgs.a} and ${validatedArgs.b} is ${sum}.`;
       return {
         content: [
           {
             type: "text",
-            text: `The sum of ${validatedArgs.a} and ${validatedArgs.b} is ${sum}.`,
+            text,
           },
         ],
+        structuredContent: { content: text }
       };
     }
 
@@ -588,24 +592,28 @@ export const createServer = () => {
         }
       }
 
+      const text = `Long running operation completed. Duration: ${duration} seconds, Steps: ${steps}.`;
       return {
         content: [
           {
             type: "text",
-            text: `Long running operation completed. Duration: ${duration} seconds, Steps: ${steps}.`,
+            text,
           },
         ],
+        structuredContent: { content: text }
       };
     }
 
     if (name === ToolName.PRINT_ENV) {
+      const text = JSON.stringify(process.env, null, 2);
       return {
         content: [
           {
             type: "text",
-            text: JSON.stringify(process.env, null, 2),
+            text,
           },
         ],
+        structuredContent: { content: text }
       };
     }
 
@@ -619,31 +627,35 @@ export const createServer = () => {
         maxTokens,
         extra.sendRequest
       );
+      const text = `LLM sampling result: ${result.content.text}`;
       return {
         content: [
-          { type: "text", text: `LLM sampling result: ${result.content.text}` },
+          { type: "text", text },
         ],
+        structuredContent: { content: text }
       };
     }
 
     if (name === ToolName.GET_TINY_IMAGE) {
       GetTinyImageSchema.parse(args);
+      const content = [
+        {
+          type: "text",
+          text: "This is a tiny image:",
+        },
+        {
+          type: "image",
+          data: MCP_TINY_IMAGE,
+          mimeType: "image/png",
+        },
+        {
+          type: "text",
+          text: "The image above is the MCP tiny image.",
+        },
+      ];
       return {
-        content: [
-          {
-            type: "text",
-            text: "This is a tiny image:",
-          },
-          {
-            type: "image",
-            data: MCP_TINY_IMAGE,
-            mimeType: "image/png",
-          },
-          {
-            type: "text",
-            text: "The image above is the MCP tiny image.",
-          },
-        ],
+        content,
+        structuredContent: { content }
       };
     }
 
@@ -695,7 +707,7 @@ export const createServer = () => {
         });
       }
 
-      return { content };
+      return { content, structuredContent: { content } };
     }
 
     if (name === ToolName.GET_RESOURCE_REFERENCE) {
@@ -709,21 +721,23 @@ export const createServer = () => {
 
       const resource = ALL_RESOURCES[resourceIndex];
 
+      const content = [
+        {
+          type: "text",
+          text: `Returning resource reference for Resource ${resourceId}:`,
+        },
+        {
+          type: "resource",
+          resource: resource,
+        },
+        {
+          type: "text",
+          text: `You can access this resource using the URI: ${resource.uri}`,
+        },
+      ];
       return {
-        content: [
-          {
-            type: "text",
-            text: `Returning resource reference for Resource ${resourceId}:`,
-          },
-          {
-            type: "resource",
-            resource: resource,
-          },
-          {
-            type: "text",
-            text: `You can access this resource using the URI: ${resource.uri}`,
-          },
-        ],
+        content,
+        structuredContent: { content }
       };
     }
 
@@ -844,7 +858,7 @@ export const createServer = () => {
         text: `\nRaw result: ${JSON.stringify(elicitationResult, null, 2)}`,
       });
 
-      return { content };
+      return { content, structuredContent: { content } };
     }
 
     if (name === ToolName.GET_RESOURCE_LINKS) {
@@ -873,7 +887,7 @@ export const createServer = () => {
         });
       }
 
-      return { content };
+      return { content, structuredContent: { content } };
     }
 
     if (name === ToolName.STRUCTURED_CONTENT) {
@@ -917,60 +931,68 @@ export const createServer = () => {
 
       const uri = `data:application/zip;base64,${await zip.generateAsync({ type: "base64" })}`;
 
+      const content = [
+        {
+          type: "resource_link",
+          mimeType: "application/zip",
+          uri,
+        },
+      ];
       return {
-        content: [
-          {
-            type: "resource_link",
-            mimeType: "application/zip",
-            uri,
-          },
-        ],
+        content,
+        structuredContent: { content }
       };
     }
 
     if (name === ToolName.LIST_ROOTS) {
       ListRootsSchema.parse(args);
 
       if (!clientSupportsRoots) {
+        const text = "The MCP client does not support the roots protocol.\n\n" +
+          "This means the server cannot access information about the client's workspace directories or file system roots.";
         return {
           content: [
             {
               type: "text",
-              text: "The MCP client does not support the roots protocol.\n\n" +
-                "This means the server cannot access information about the client's workspace directories or file system roots."
+              text
             }
-          ]
+          ],
+          structuredContent: { content: text }
         };
       }
 
       if (currentRoots.length === 0) {
+        const text = "The client supports roots but no roots are currently configured.\n\n" +
+          "This could mean:\n" +
+          "1. The client hasn't provided any roots yet\n" +
+          "2. The client provided an empty roots list\n" +
+          "3. The roots configuration is still being loaded";
         return {
           content: [
             {
               type: "text",
-              text: "The client supports roots but no roots are currently configured.\n\n" +
-                "This could mean:\n" +
-                "1. The client hasn't provided any roots yet\n" +
-                "2. The client provided an empty roots list\n" +
-                "3. The roots configuration is still being loaded"
+              text
             }
-          ]
+          ],
+          structuredContent: { content: text }
         };
       }
 
       const rootsList = currentRoots.map((root, index) => {
         return `${index + 1}. ${root.name || 'Unnamed Root'}\n   URI: ${root.uri}`;
       }).join('\n\n');
 
+      const text = `Current MCP Roots (${currentRoots.length} total):\n\n${rootsList}\n\n` +
+        "Note: This server demonstrates the roots protocol capability but doesn't actually access files. " +
+        "The roots are provided by the MCP client and can be used by servers that need file system access.";
       return {
         content: [
           {
             type: "text",
-            text: `Current MCP Roots (${currentRoots.length} total):\n\n${rootsList}\n\n` +
-              "Note: This server demonstrates the roots protocol capability but doesn't actually access files. " +
-              "The roots are provided by the MCP client and can be used by servers that need file system access."
+            text
           }
-        ]
+        ],
+        structuredContent: { content: text }
       };
     }