[MCP] Support object body param and Abilities API guidance

packages/playground/mcp/src/tools/register-mcp-server-tools.ts

@@ -55,6 +55,9 @@ function paramsToZodSchema(params: ToolParam[]): Record<string, z.ZodType> {
 			case 'object':
 				zodType = z.record(z.string(), z.string());
 				break;
+			case 'string_or_object':
+				zodType = z.union([z.string(), z.record(z.string(), z.unknown())]);
+				break;
 			default:
 				throw new Error(
 					`Unknown param type "${param.type}" for "${param.name}"`

packages/playground/mcp/src/tools/tool-definitions.ts

@@ -13,7 +13,7 @@ export interface ToolAnnotations {
 	openWorldHint?: boolean;
 }
 
-export type ToolParamType = 'string' | 'boolean' | 'object';
+export type ToolParamType = 'string' | 'boolean' | 'object' | 'string_or_object';
 
 export interface ToolParam {
 	name: string;
@@ -90,19 +90,17 @@ export const toolDefinitions: Record<string, ToolDefinition> = {
 			auth needed.
 
 			Tool selection guide:
-			1. Use this tool (playground_request) with the
-			   REST API for standard content CRUD — posts,
-			   pages, users, terms, comments, settings, etc.
-			   The REST API handles serialization, pagination,
-			   and field filtering for you.
+			1. Use this tool with the REST API for content
+			   CRUD (posts, pages, users, settings, etc.)
+			   and for the Abilities API
+			   (/wp-json/wp-abilities/v1/abilities) which
+			   exposes structured actions from plugins and
+			   WordPress core.
 			2. Use playground_execute_php when the data you
-			   need is not exposed by the REST API (e.g.
-			   raw options, direct database queries, or
-			   custom table access).
+			   need is not exposed by the REST API.
 			3. Use this tool as a plain HTTP request (non-REST)
-			   when the HTTP layer itself matters: verifying
-			   redirects, status codes, cookies, or response
-			   headers.
+			   when the HTTP layer itself matters (redirects,
+			   status codes, cookies, headers).
 
 			The response JSON contains three fields:
 			- "text": the response body as a string
@@ -147,8 +145,8 @@ export const toolDefinitions: Record<string, ToolDefinition> = {
 			},
 			{
 				name: 'body',
-				type: 'string',
-				description: 'Request body (for POST/PUT requests)',
+				type: 'string_or_object',
+				description: 'Request body (for POST/PUT requests). Accepts a JSON string or an object.',
 				required: false,
 			},
 		],
@@ -531,10 +529,13 @@ export function paramsToJsonSchema(
 	const required: string[] = [];
 
 	for (const param of params) {
-		const prop: Record<string, unknown> = {
-			type: param.type,
-			description: param.description,
-		};
+		const prop: Record<string, unknown> = {};
+		if (param.type === 'string_or_object') {
+			prop['oneOf'] = [{ type: 'string' }, { type: 'object' }];
+		} else {
+			prop['type'] = param.type;
+		}
+		prop['description'] = param.description;
 		if (param.additionalProperties !== undefined) {
 			prop['additionalProperties'] = param.additionalProperties;
 		}

packages/playground/mcp/src/tools/tool-executors.ts

@@ -97,7 +97,11 @@ export const toolExecutors: Record<
 		const headers = {
 			...((input['headers'] as Record<string, string>) ?? {}),
 		};
-		const body = input['body'] as string | undefined;
+		const rawBody = input['body'];
+		const body =
+			typeof rawBody === 'object' && rawBody !== null
+				? JSON.stringify(rawBody)
+				: (rawBody as string | undefined);
 
 		try {
 			const parsedUrl = new URL(url, 'http://localhost');

packages/playground/mcp/tests/e2e/mcp-tools.spec.ts

@@ -762,6 +762,39 @@ test.describe.serial('playground_request REST API auth', () => {
 		expect(JSON.parse(gone.text).code).toBe('rest_post_invalid_id');
 	});
 
+	test('accepts object body without JSON.stringify', async ({
+		mcpClient,
+		siteId,
+	}) => {
+		const createResult = await mcpClient.callTool({
+			name: 'playground_request',
+			arguments: {
+				siteId,
+				url: '/wp-json/wp/v2/posts',
+				method: 'POST',
+				body: {
+					title: 'Object Body Test',
+					content: 'Created with object body',
+					status: 'publish',
+				},
+			},
+		});
+		const created = JSON.parse(resultText(createResult));
+		expect(created.httpStatusCode).toBe(201);
+		const post = JSON.parse(created.text);
+		expect(post.title.raw).toBe('Object Body Test');
+
+		// Clean up
+		await mcpClient.callTool({
+			name: 'playground_request',
+			arguments: {
+				siteId,
+				url: `/wp-json/wp/v2/posts/${post.id}?force=true`,
+				method: 'DELETE',
+			},
+		});
+	});
+
 	test('logged-out user cannot create posts', async ({
 		mcpClient,
 		siteId,