make content required

src/examples/client/parallelToolCallsClient.ts

@@ -61,7 +61,7 @@ async function main(): Promise<void> {
     // Log the results from each tool call
     for (const [caller, result] of Object.entries(toolResults)) {
       console.log(`\n=== Tool result for ${caller} ===`);
-      result.content?.forEach((item: { type: string; text?: string; }) => {
+      result.content.forEach((item: { type: string; text?: string; }) => {
         if (item.type === 'text') {
           console.log(`  ${item.text}`);
         } else {

src/examples/client/simpleStreamableHttp.ts

@@ -264,12 +264,12 @@ async function terminateSession(): Promise<void> {
     console.log('Terminating session with ID:', transport.sessionId);
     await transport.terminateSession();
     console.log('Session terminated successfully');
-    
+
     // Check if sessionId was cleared after termination
     if (!transport.sessionId) {
       console.log('Session ID has been cleared');
       sessionId = undefined;
-      
+
       // Also close the transport and clear client objects
       await transport.close();
       console.log('Transport closed after session termination');
@@ -341,7 +341,7 @@ async function callTool(name: string, args: Record<string, unknown>): Promise<vo
     });
 
     console.log('Tool result:');
-    result.content?.forEach(item => {
+    result.content.forEach(item => {
       if (item.type === 'text') {
         console.log(`  ${item.text}`);
       } else {
@@ -456,7 +456,7 @@ async function cleanup(): Promise<void> {
           console.error('Error terminating session:', error);
         }
       }
-      
+
       // Then close the transport
       await transport.close();
     } catch (error) {

src/examples/client/streamableHttpWithSseFallbackClient.ts

@@ -173,7 +173,7 @@ async function startNotificationTool(client: Client): Promise<void> {
     const result = await client.request(request, CallToolResultSchema);
 
     console.log('Tool result:');
-    result.content?.forEach(item => {
+    result.content.forEach(item => {
       if (item.type === 'text') {
         console.log(`  ${item.text}`);
       } else {

src/examples/server/mcpServerOutputSchema.ts

@@ -20,7 +20,7 @@ server.registerTool(
   "get_weather",
   {
     description: "Get weather information for a city",
-    inputSchema:{
+    inputSchema: {
       city: z.string().describe("City name"),
       country: z.string().describe("Country code (e.g., US, UK)")
     },
@@ -46,10 +46,11 @@ server.registerTool(
     const conditions = ["sunny", "cloudy", "rainy", "stormy", "snowy"][Math.floor(Math.random() * 5)];
 
     return {
+      content: [],
       structuredContent: {
         temperature: {
           celsius: temp_c,
-          fahrenheit: Math.round((temp_c * 9/5 + 32) * 10) / 10
+          fahrenheit: Math.round((temp_c * 9 / 5 + 32) * 10) / 10
         },
         conditions,
         humidity: Math.round(Math.random() * 100),

src/server/mcp.test.ts

@@ -398,7 +398,7 @@ describe("tool()", () => {
         name: z.string(),
         value: z.number(),
       },
-      callback: async ({name, value}) => ({
+      callback: async ({ name, value }) => ({
         content: [
           {
             type: "text",
@@ -729,7 +729,7 @@ describe("tool()", () => {
     });
 
     mcpServer.tool(
-      "test", 
+      "test",
       { name: z.string() },
       { title: "Test Tool", readOnlyHint: true },
       async ({ name }) => ({
@@ -787,7 +787,7 @@ describe("tool()", () => {
     });
 
     mcpServer.tool(
-      "test", 
+      "test",
       "A tool with everything",
       { name: z.string() },
       { title: "Complete Test Tool", readOnlyHint: true, openWorldHint: false },
@@ -828,8 +828,8 @@ describe("tool()", () => {
       type: "object",
       properties: { name: { type: "string" } }
     });
-    expect(result.tools[0].annotations).toEqual({ 
-      title: "Complete Test Tool", 
+    expect(result.tools[0].annotations).toEqual({
+      title: "Complete Test Tool",
       readOnlyHint: true,
       openWorldHint: false
     });
@@ -853,7 +853,7 @@ describe("tool()", () => {
     });
 
     mcpServer.tool(
-      "test", 
+      "test",
       "A tool with everything but empty params",
       {},
       { title: "Complete Test Tool with empty params", readOnlyHint: true, openWorldHint: false },
@@ -894,8 +894,8 @@ describe("tool()", () => {
       type: "object",
       properties: {}
     });
-    expect(result.tools[0].annotations).toEqual({ 
-      title: "Complete Test Tool with empty params", 
+    expect(result.tools[0].annotations).toEqual({
+      title: "Complete Test Tool with empty params",
       readOnlyHint: true,
       openWorldHint: false
     });
@@ -1077,9 +1077,9 @@ describe("tool()", () => {
           input: z.string(),
         },
         outputSchema: {
-            processedInput: z.string(),
-            resultType: z.string(),
-            timestamp: z.string()
+          processedInput: z.string(),
+          resultType: z.string(),
+          timestamp: z.string()
         },
       },
       async ({ input }) => ({
@@ -1088,6 +1088,16 @@ describe("tool()", () => {
           resultType: "structured",
           timestamp: "2023-01-01T00:00:00Z"
         },
+        content: [
+          {
+            type: "text",
+            text: JSON.stringify({
+              processedInput: input,
+              resultType: "structured",
+              timestamp: "2023-01-01T00:00:00Z"
+            }),
+          },
+        ]
       })
     );
 
@@ -1186,6 +1196,17 @@ describe("tool()", () => {
         },
       },
       async ({ input }) => ({
+        content: [
+          {
+            type: "text",
+            text: JSON.stringify({
+              processedInput: input,
+              resultType: "structured",
+              // Missing required 'timestamp' field
+              someExtraField: "unexpected" // Extra field not in schema
+            }),
+          },
+        ],
         structuredContent: {
           processedInput: input,
           resultType: "structured",
@@ -2664,7 +2685,7 @@ describe("prompt()", () => {
         name: z.string(),
         value: z.string(),
       },
-      callback: async ({name, value}) => ({
+      callback: async ({ name, value }) => ({
         messages: [
           {
             role: "assistant",

src/types.ts

@@ -843,13 +843,13 @@ export const ToolSchema = z
      * If not set, a CallToolResult for this Tool MUST NOT contain a structuredContent field and MUST contain a content field.
      */
     outputSchema: z.optional(
-        z.object({
-          type: z.literal("object"),
-          properties: z.optional(z.object({}).passthrough()),
-          required: z.optional(z.array(z.string())),
-        })
+      z.object({
+        type: z.literal("object"),
+        properties: z.optional(z.object({}).passthrough()),
+        required: z.optional(z.array(z.string())),
+      })
         .passthrough()
-      ),
+    ),
     /**
      * Optional additional tool information.
      */
@@ -892,46 +892,21 @@ export const ContentListSchema = z.array(
   ]),
 );
 
-export const CallToolUnstructuredResultSchema = ResultSchema.extend({
+export const CallToolResultSchema = ResultSchema.extend({
   /**
    * A list of content objects that represent the result of the tool call.
    *
    * If the Tool does not define an outputSchema, this field MUST be present in the result.
+   * For backwards compatibility, this field is always present, but it may be empty.
    */
-  content: ContentListSchema,
+  content: ContentListSchema.default([]),
 
-  /**
-   * Structured output must not be provided in an unstructured tool result.
-   */
-  structuredContent: z.never().optional(),
-
-  /**
-   * Whether the tool call ended in an error.
-   *
-   * If not set, this is assumed to be false (the call was successful).
-   */
-  isError: z.optional(z.boolean()),
-});
-
-export const CallToolStructuredResultSchema = ResultSchema.extend({
   /**
    * An object containing structured tool output.
    *
    * If the Tool defines an outputSchema, this field MUST be present in the result, and contain a JSON object that matches the schema.
    */
-  structuredContent: z.object({}).passthrough(),
-
-  /**
-   * A list of content objects that represent the result of the tool call.
-   *
-   * If the Tool defines an outputSchema, this field MAY be present in the result.
-   * 
-   * Tools may use this field to provide compatibility with older clients that 
-   * do not support structured content.
-   * 
-   * Clients that support structured content should ignore this field.
-   */
-  content: z.optional(ContentListSchema),
+  structuredContent: z.object({}).passthrough().optional(),
 
   /**
    * Whether the tool call ended in an error.
@@ -941,11 +916,6 @@ export const CallToolStructuredResultSchema = ResultSchema.extend({
   isError: z.optional(z.boolean()),
 });
 
-export const CallToolResultSchema = z.union([
-  CallToolUnstructuredResultSchema,
-  CallToolStructuredResultSchema,
-]);
-
 /**
  * CallToolResultSchema extended with backwards compatibility to protocol version 2024-10-07.
  */
@@ -1397,8 +1367,6 @@ export type Tool = Infer<typeof ToolSchema>;
 export type ListToolsRequest = Infer<typeof ListToolsRequestSchema>;
 export type ListToolsResult = Infer<typeof ListToolsResultSchema>;
 export type ContentList = Infer<typeof ContentListSchema>;
-export type CallToolUnstructuredResult = Infer<typeof CallToolUnstructuredResultSchema>;
-export type CallToolStructuredResult = Infer<typeof CallToolStructuredResultSchema>;
 export type CallToolResult = Infer<typeof CallToolResultSchema>;
 export type CompatibilityCallToolResult = Infer<typeof CompatibilityCallToolResultSchema>;
 export type CallToolRequest = Infer<typeof CallToolRequestSchema>;