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Python
Local

s3_download_object

Download an S3 object to a local file, restricting writes to your home directory, current working directory, or ~/Downloads for safety.

Instructions

Download an object from S3 to a local file. local_path must resolve under the user's home directory, current working directory, or ~/Downloads — paths outside these roots are rejected for safety.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
keyYesObject key.
bucketYesBucket name.
regionNoRegion the bucket lives in (e.g. 'eu-central-1'). Omit unless you know it — it is resolved automatically. AWS, and OVH when no endpoint URL is configured (pass the region s3_list_buckets reports). Rejected for Hetzner, and for an OVH endpoint URL set by hand, whose region is fixed by that endpoint.
accountNoAccount label of the provider whose object storage to use; omit for that provider's default account.
providerYesStorage provider.
local_pathYesLocal file path to write the downloaded object to.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv2.28.0
    • addedInput schema / properties / account
      Added value: +{
+  "description": "Account label of the provider whose object storage to use; omit for that provider's default account.",
+  "type": "string"
+}
    • changedInput schema / properties / region / description
      Previous value: -"Region the bucket lives in (e.g. 'eu-central-1'). Omit unless you know it — it is resolved automatically. AWS only; rejected for Hetzner/OVH, whose region is fixed by the configured endpoint URL."New value: +"Region the bucket lives in (e.g. 'eu-central-1'). Omit unless you know it — it is resolved automatically. AWS, and OVH when no endpoint URL is configured (pass the region s3_list_buckets reports). Rejected for Hetzner, and for an OVH endpoint URL set by hand, whose region is fixed by that endpoint."
  2. Changed1 schema field changedv2.24.2
    • addedInput schema / properties / region
      Added value: +{
+  "description": "Region the bucket lives in (e.g. 'eu-central-1'). Omit unless you know it — it is resolved automatically. AWS only; rejected for Hetzner/OVH, whose region is fixed by the configured endpoint URL.",
+  "type": "string"
+}
  3. Addedv2.24.0
  4. Removedv2.23.8
  5. First observedv1.0.0

TDQS

A3.9/5.0
Behavior3/5

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

With no annotations, the description carries the full burden, and it usefully discloses a real behavioral trait: local_path must resolve under home, cwd, or ~/Downloads, and outside paths are rejected. However it omits other salient behavior such as overwrite handling, size/streaming limits, and authentication needs for the download itself.

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?

Two tight sentences, with the core action front-loaded and the safety constraint following. No filler or redundancy.

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

Completeness3/5

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

There is no output schema and no annotations, so the description must carry more weight; it covers the critical path-safety constraint but says nothing about the return value or success/failure signaling. Adequate but with clear gaps for a download tool.

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?

Schema coverage is 100%, so the baseline is 3, but the description adds genuine semantic meaning not in the schema by explaining the resolution constraint and rejection behavior for local_path. It does not elaborate on bucket/key/region beyond the already-rich schema.

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?

States a specific verb (Download) with resource (object from S3) and destination (local file), which is unambiguous against siblings like s3_upload_object and s3_copy_object. An agent can tell exactly what this does without opening the schema.

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 path-safety constraint gives practical context for invoking it, but there is no explicit when-to-use guidance or routing against alternatives (e.g., when to prefer s3_copy_object for server-side copies). Usage is implied by the verb rather than stated.

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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