Playwright MCP Server

Instructions

Implementation Reference

• src/tools/browser/response.ts:21-44 (handler)

  ExpectResponseTool class with execute method that initiates page.waitForResponse(url) and stores the promise in a map keyed by the provided id.

  export class ExpectResponseTool extends BrowserToolBase {
    /**
     * Execute the expect response tool
     */
    async execute(
      args: ExpectResponseArgs,
      context: ToolContext
    ): Promise<ToolResponse> {
      return this.safeExecute(context, async (page) => {
        if (!args.id || !args.url) {
          return createErrorResponse(
            "Missing required parameters: id and url must be provided"
          );
        }
  
        const responsePromise = page.waitForResponse(args.url);
        responsePromises.set(args.id, responsePromise);
  
        return createSuccessResponse(
          `Started waiting for response with ID ${args.id}`
        );
      });
    }
  }

• src/tools.ts:282-293 (schema)

  Tool schema definition specifying input parameters 'id' (string) and 'url' (string).

  {
    name: "playwright_expect_response",
    description: "Ask Playwright to start waiting for a HTTP response. This tool initiates the wait operation but does not wait for its completion.",
    inputSchema: {
      type: "object",
      properties: {
        id: { type: "string", description: "Unique & arbitrary identifier to be used for retrieving this response later with `Playwright_assert_response`." },
        url: { type: "string", description: "URL pattern to match in the response." }
      },
      required: ["id", "url"],
    },
  },

• src/toolHandler.ts:486-487 (registration)

  Registration in the main tool handler switch statement, delegating execution to ExpectResponseTool instance.

  case "playwright_expect_response":
    return await expectResponseTool.execute(args, context);

• src/toolHandler.ts:296-296 (registration)

  Instantiation of the ExpectResponseTool class instance used by the handler.

  if (!expectResponseTool) expectResponseTool = new ExpectResponseTool(server);

• src/tools/codegen/generator.ts:125-130 (helper)

  Helper method in codegen generator to produce Playwright test code for this tool.

  private generateExpectResponseStep(parameters: Record<string, unknown>): string {
    const { url, id } = parameters;
    return `
    // Wait for response
    const ${id}Response = page.waitForResponse('${url}');`;
  }