Browserless MCP Server

Instructions

Implementation Reference

• src/index.ts:135-146 (registration)

  Registration of the 'execute_function' tool including name, description, and input schema in the ListTools response.

  {
    name: 'execute_function',
    description: 'Execute custom JavaScript function in browser context',
    inputSchema: {
      type: 'object',
      properties: {
        code: { type: 'string' },
        context: { type: 'object' },
      },
      required: ['code'],
    },
  },

• src/index.ts:370-389 (handler)

  The main handler for the 'execute_function' tool in the MCP server, which calls the BrowserlessClient.executeFunction and formats the response as MCP content.

  case 'execute_function': {
    if (!args) throw new Error('Arguments are required');
    const result = await this.client!.executeFunction(args as any);
    if (result.success && result.data) {
      return {
        content: [
          {
            type: 'text',
            text: `Function executed successfully. Result type: ${result.data.type}`,
          },
          {
            type: 'text',
            text: JSON.stringify(result.data.result, null, 2),
          },
        ],
      };
    } else {
      throw new Error(result.error || 'Failed to execute function');
    }
  }

• src/client.ts:129-144 (helper)

  Helper method in BrowserlessClient that performs the actual HTTP POST request to the Browserless server '/function' endpoint to execute the provided JavaScript code.

  async executeFunction(request: FunctionRequest): Promise<BrowserlessResponse<FunctionResponse>> {
    try {
      const response: AxiosResponse<FunctionResponse> = await this.httpClient.post('/function', request, {
        headers: {
          'Content-Type': 'application/javascript',
        },
      });
  
      return {
        success: true,
        data: response.data,
      };
    } catch (error) {
      return this.handleError(error);
    }
  }