@atengk/mcp-server-s3

download_file

Streams an S3 object to a local file inside the workspace sandbox, using the object key and destination path.

Instructions

S3 对象流式保存为本地文件（受本地工作区沙箱保护）

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": {
      "key": "<key>",
      "local_path": "<local_path>"
    },
    "name": "download_file"
  }
}

Input Schema

Name	Required	Description	Default
`key`	Yes
`bucket`	No
`local_path`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Oct 4, 2026

TDQS

C2.7/5.0

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. The sandbox note is genuinely useful context, but it omits whether the file is overwritten, whether directories are created, permission/auth requirements, and streaming/size limits — significant gaps for a tool that writes to disk.

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 front-loaded sentence with no filler. It is appropriately terse, though the brevity is partly under-specification rather than pure economy.

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?

With no annotations, no output schema, and 0% parameter coverage, the description should do far more work. It establishes the action and the sandbox constraint but leaves behavior, parameters, and result handling undocumented.

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 explains none of the three parameters. It does not clarify the relationship between 'key' and the optional 'bucket', or what 'local_path' is relative to (presumably the sandbox root), leaving the agent to guess.

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 gives a clear verb+resource: streaming an S3 object into a local file, with the sandbox qualifier adding scope. It is distinguishable from siblings like upload_file and read_object_text, though it never names them 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?

There is no guidance on when to choose this over read_object_text, read_object_range, or get_presigned_url, nor any stated prerequisites. The agent must infer the use case from the name alone.

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