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get_instances

Retrieve all active Scrapybara MCP server instances to manage virtual Ubuntu desktops for web browsing, code execution, and system control.

Instructions

Get all running Scrapybara instances.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • Handler function for the 'get_instances' tool within the CallToolRequestSchema request handler. It creates a ScrapybaraClient, calls getInstances() with abort signal, and returns the instances as JSON-formatted text content.
    case "get_instances": {
      const instances = await client.getInstances({
        abortSignal: currentController.signal,
      });
    
      return {
        content: [
          {
            type: "text",
            text: JSON.stringify(instances, null, 2),
          } as TextContent,
        ],
      };
    }
  • Zod schema definition for the 'get_instances' tool input, which is an empty object indicating no input parameters are required.
    export const GetInstancesSchema = z.object({});
  • src/index.ts:78-82 (registration)
    Registration of the 'get_instances' tool in the ListToolsRequestSchema handler, including name, description, and input schema reference.
    {
      name: "get_instances",
      description: "Get all running Scrapybara instances.",
      inputSchema: zodToJsonSchema(GetInstancesSchema),
    },
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It states what the tool does but lacks behavioral details such as whether it requires authentication, how it handles errors, or what the return format looks like. This is a significant gap for a tool with zero annotation coverage.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence with no wasted words. It's front-loaded and directly states the tool's purpose without unnecessary elaboration.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no annotations and no output schema, the description is incomplete. It lacks details on behavioral traits, return values, or error handling, which are crucial for a tool that likely interacts with system resources like instances.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has 0 parameters, and schema description coverage is 100%, so no parameter information is needed. The description doesn't add param details, but that's appropriate here, meeting the baseline for zero parameters.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb ('Get') and resource ('all running Scrapybara instances'), making the purpose unambiguous. It doesn't explicitly differentiate from siblings like 'start_instance' or 'stop_instance', but the action is distinct enough to imply differentiation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided on when to use this tool versus alternatives like 'start_instance' or 'stop_instance'. The description implies usage for listing instances but doesn't specify prerequisites, timing, or exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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