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Code Gym AWS Emulator MCP

Code Gym AWS Emulator MCP

by B11-Health
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

s3_list_objects

Read-onlyIdempotent

Lists object keys in an emulated S3 bucket so you can inspect local sandbox contents and verify test data without an AWS account.

Instructions

List keys in emulated S3 bucket

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "bucket": "<bucket>"
    },
    "name": "s3_list_objects"
  }
}

Input Schema

NameRequiredDescriptionDefault
bucketYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.4.0-beta.1

TDQS

C2.7/5.0
Behavior2/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description's only added context is the word 'emulated', which usefully signals this targets a local emulator rather than real AWS; it says nothing about pagination, truncation, result ordering, or whether large buckets are capped, which matters for a list operation.

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

Conciseness4/5

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

A single compact phrase with the resource front-loaded and no filler. Nothing superfluous, though its brevity reflects under-specification rather than tight editing.

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?

For a list tool with no output schema, the description should say what comes back (key names only? objects with metadata?) and how to handle large buckets. Neither is covered, and the sole parameter is undocumented, leaving real gaps for correct invocation.

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

Parameters2/5

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

The single 'bucket' parameter has 0% schema description coverage, so the description must carry the burden. It only implies that the parameter names the bucket to list from and adds nothing about expected naming format, whether a prefix/delimiter filter is supported, or any constraints.

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?

States a specific verb and resource: 'List keys' in an 'emulated S3 bucket'. 'Keys' rather than 'buckets' implicitly distinguishes it from the s3_list_buckets sibling, though no sibling is named explicitly.

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 when-to-use guidance, no prerequisites, and no mention of the obvious alternative (s3_list_buckets for enumerating buckets, s3_get_object for reading a key). The agent must infer the division of labor from the sibling name alone.

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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