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s3-mcp

s3-mcp

by JakePeralta7
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

stat_object

Read-only

Retrieve S3 object metadata, including size, ETag, content type, and last modified time, to verify file details.

Instructions

Get object metadata (size, etag, content type, last modified).

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>",
      "key": "<key>"
    },
    "name": "stat_object"
  }
}

Input Schema

NameRequiredDescriptionDefault
keyYes
bucketYes

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.7/5.0
Behavior3/5

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

The readOnlyHint annotation is present, and the description's 'Get' is consistent. The description adds the specific metadata fields returned but does not disclose other behaviors like whether it fails on missing objects or that it does not transfer data. Since annotations cover the read-only aspect, the description adds moderate context but not rich behavioral detail.

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 concise sentence that front-loads the verb and purpose. It includes the key metadata fields without any wasted words.

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

Completeness4/5

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

For a simple metadata retrieval tool with an output schema and read-only annotation, the description covers the essential purpose and return fields. It could be more explicit about not retrieving the object content, but given the simplicity and existing schema, it is largely complete.

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?

Schema description coverage is 0% and the description does not explain the 'bucket' and 'key' parameters. It only lists the metadata fields. Since the schema has no descriptions, the description fails to compensate, leaving the agent to infer the meaning of the parameters from their names alone.

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

Purpose5/5

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

The description clearly states the verb 'Get' and the resource 'object metadata', listing specific fields (size, etag, content type, last modified). This distinguishes it from siblings like get_object which retrieves content, and list_objects which lists objects.

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

Usage Guidelines3/5

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

The description does not explicitly state when to use this tool versus alternatives. It implies it is for metadata-only retrieval, but does not mention get_object or other siblings, nor any conditions for when to use it. Guidance is only implied by the purpose.

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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