fix: treat empty object as raw shape (matches v1); drop stale changeset claims

Author: felixweinberger

.changeset/mcpserver-variadic-compat.md

@@ -2,4 +2,4 @@
 '@modelcontextprotocol/server': patch
 ---
 
-Restore `McpServer.tool()`, `.prompt()`, `.resource()` variadic overloads as `@deprecated` v1-compat shims forwarding to `registerTool`/`registerPrompt`/`registerResource`. Emits a one-time deprecation warning; removed in v3.
+Restore `McpServer.tool()`, `.prompt()`, `.resource()` variadic overloads as `@deprecated` v1-compat shims forwarding to `registerTool`/`registerPrompt`/`registerResource`.

packages/server/src/server/mcp.ts

@@ -1219,8 +1219,8 @@ export type LegacyPromptCallback<Args extends ZodRawShape | undefined> = Args ex
 function isZodRawShape(obj: unknown): obj is ZodRawShape {
     if (typeof obj !== 'object' || obj === null) return false;
     if (isStandardSchema(obj)) return false;
-    const values = Object.values(obj);
-    return values.length > 0 && values.every(v => isStandardSchema(v));
+    // [].every() is true, so an empty object is a valid raw shape (matches v1).
+    return Object.values(obj).every(v => isStandardSchema(v));
 }
 
 /**

packages/server/test/server/mcp.compat.test.ts

@@ -33,6 +33,13 @@ describe('McpServer v1-compat variadic shims', () => {
             const reg = server.tool('x', () => ({ content: [{ type: 'text', text: 'ok' }] }));
             expect(reg.inputSchema).toBeUndefined();
         });
+
+        it('treats empty object as raw shape, not annotations (matches v1)', () => {
+            const server = new McpServer({ name: 't', version: '1' });
+            const reg = server.tool('x', {}, () => ({ content: [{ type: 'text', text: 'ok' }] }));
+            expect(reg.inputSchema).toBeDefined();
+            expect(reg.annotations).toBeUndefined();
+        });
     });
 
     describe('.prompt()', () => {