Scrapybara MCP

Instructions

Implementation Reference

• src/index.ts:206-242 (handler)

  Handler for the 'act' tool: parses input with ActSchema, retrieves the Scrapybara instance, sets up tools (computer, bash, edit), calls client.act with model, system prompt, prompt, and schema, then returns the response.

  case "act": {
    const args = ActSchema.parse(request.params.arguments);
    const instance = await client.get(args.instance_id, {
      abortSignal: currentController.signal,
    });
  
    const tools: Scrapybara.Tool[] = [computerTool(instance)];
  
    if (instance instanceof UbuntuInstance) {
      tools.push(bashTool(instance));
      tools.push(editTool(instance));
    }
  
    const actResponse = await client.act({
      model: actModel,
      tools,
      system: actSystem,
      prompt: args.prompt,
      schema: args.schema,
      requestOptions: {
        abortSignal: currentController.signal,
      },
    });
  
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(
            { text: actResponse.text, output: actResponse.output },
            null,
            2
          ),
        } as TextContent,
      ],
    };
  }

• src/schemas.ts:25-38 (schema)

  Zod schema for 'act' tool inputs: instance_id (string), prompt (string with examples), schema (optional any).

  export const ActSchema = z.object({
    instance_id: z.string().describe("The ID of the instance to act on."),
    prompt: z.string().describe(`The prompt to act on.
  <EXAMPLES>
  - Go to https://ycombinator.com/companies, set batch filter to W25, and extract all company names.
  - Find the best way to contact Scrapybara.
  - Order a Big Mac from McDonald's on Doordash.
  </EXAMPLES>
  `),
    schema: z
      .any()
      .optional()
      .describe("Optional schema if you want to extract structured output."),
  });

• src/index.ts:93-98 (registration)

  Tool registration for 'act' in the ListToolsRequestHandler response, including name, description, and inputSchema from ActSchema.

  {
    name: "act",
    description:
      "Take action on a Scrapybara instance through an agent. The agent can control the instance with mouse/keyboard and bash commands.",
    inputSchema: zodToJsonSchema(ActSchema),
  },

• src/index.ts:33-45 (helper)

  Helper variables configuring the model and system prompt for the 'act' tool based on ACT_MODEL environment variable.

  let actModel =
    process.env.ACT_MODEL === "anthropic"
      ? anthropic()
      : process.env.ACT_MODEL === "openai"
      ? openai()
      : anthropic(); // Default to Anthropic
  
  let actSystem =
    process.env.ACT_MODEL === "anthropic"
      ? ANTHROPIC_UBUNTU_SYSTEM_PROMPT
      : process.env.ACT_MODEL === "openai"
      ? OPENAI_UBUNTU_SYSTEM_PROMPT
      : ANTHROPIC_UBUNTU_SYSTEM_PROMPT; // Default to Anthropic's prompt