fix: retain required request bodies without schema constraints

test/required-unconstrained-body.test.ts

@@ -0,0 +1,20 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import type { OpenAPIV3 } from 'openapi-types';
+import { init } from '../vendor/forge/index.js';
+import { buildManifest } from '../src/manifest.js';
+
+for (const schema of [{ type: 'object' }, {}]) {
+  test(`required unconstrained JSON body is not discarded: ${JSON.stringify(schema)}`, async () => {
+    const doc = { openapi: '3.0.3', info: { title: 'Required body', version: '1' }, components: { schemas: {} },
+      paths: { '/x': { post: { operationId: 'x', requestBody: { required: true, content: { 'application/json': { schema } } },
+        responses: { '204': { description: 'OK' } } } } },
+    } as unknown as OpenAPIV3.Document;
+    await init(doc);
+    const tool = buildManifest(doc).tools[0]!;
+    assert.equal(tool.contentType, 'application/json');
+    assert.deepEqual(tool.inputSchema.required, ['body']);
+    assert.equal(tool.args[0]?.required, true);
+    assert.deepEqual(tool.args[0]?.apiFieldPath, []);
+  });
+}

vendor/forge/openapi-resolver.ts

@@ -41,6 +41,7 @@ interface PathItem {
 }
 
 interface RequestBody {
+  required?: boolean;
   /** Reference to a `#/components/requestBodies/...` entry, if applicable. */
   $ref?: string;
   /** Human-readable description of the request body. */
@@ -647,6 +648,8 @@ export function normalizedRequestBody<T>(value: T): T {
 }
 
 function isSemanticallyEmptyRequestBody(requestBody: RequestBody): boolean {
+  // A required body still needs a wire representation even without constraints.
+  if (requestBody.required === true) return false;
   const content = requestBody.content;
   if (!content) return false;
   const mediaEntries = Object.entries(content);