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bash

Execute bash commands on Scrapybara virtual Ubuntu instances to run code, automate tasks, and control remote environments through shell operations.

Instructions

Run a bash command in a Scrapybara instance.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
instance_idYesThe ID of the instance to run the command on.
commandYesThe command to run in the instance shell.

Implementation Reference

  • Handler for the 'bash' MCP tool: parses arguments using BashSchema, retrieves Scrapybara instance, calls instance.bash(command), and returns the response.
    case "bash": {
      const args = BashSchema.parse(request.params.arguments);
      const instance = await client.get(args.instance_id, {
        abortSignal: currentController.signal,
      });
    
      if ("bash" in instance) {
        const response = await instance.bash(
          { command: args.command },
          { abortSignal: currentController.signal }
        );
    
        return {
          content: [
            {
              type: "text",
              text: JSON.stringify(response, null, 2),
            } as TextContent,
          ],
        };
      } else {
        throw new Error("Instance does not support bash commands");
      }
    }
  • Zod schema defining input for bash tool: instance_id (string) and command (string). Used for validation in handler and JSON schema in registration.
    export const BashSchema = z.object({
      instance_id: z
        .string()
        .describe("The ID of the instance to run the command on."),
      command: z.string().describe("The command to run in the instance shell."),
    });
  • src/index.ts:89-92 (registration)
    Tool registration in listTools response: defines name 'bash', description, and input schema derived from BashSchema.
      name: "bash",
      description: "Run a bash command in a Scrapybara instance.",
      inputSchema: zodToJsonSchema(BashSchema),
    },
Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the action but doesn't reveal critical traits like whether this is a read-only or destructive operation, potential security implications, rate limits, or error handling. For a tool that runs arbitrary commands, this lack of transparency is a significant gap.

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 that directly states the tool's purpose without unnecessary words. It is front-loaded and wastes no space, making it easy to parse quickly.

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 the complexity of running arbitrary bash commands and the absence of annotations and output schema, the description is incomplete. It doesn't cover behavioral aspects like safety, permissions, or output format, which are crucial for such a tool. This leaves the agent with insufficient context for reliable use.

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

Parameters3/5

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

The input schema has 100% description coverage, clearly documenting both parameters ('instance_id' and 'command'). The description adds no additional meaning beyond what the schema provides, such as command syntax examples or instance state requirements. Baseline 3 is appropriate since the schema does the heavy lifting.

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 action ('Run') and target ('bash command in a Scrapybara instance'), making the purpose understandable. However, it doesn't differentiate from sibling tools like 'act' or 'start_instance', which might also involve instance operations, leaving some ambiguity about when this specific tool is appropriate versus others.

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?

The description provides no guidance on when to use this tool versus alternatives like 'act' or 'start_instance'. It lacks context about prerequisites, such as whether the instance must be running, or exclusions, such as not using it for non-bash commands. This leaves the agent without clear usage instructions.

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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