Generate a pre-signed GET URL for accessing private S3 objects. Specify bucket, key, and expiration time (up to 604800 seconds) to grant temporary read access.
Generate a pre-signed GET URL valid for expires_s seconds (max 604800).
| Name | Required | Description | Default |
|---|---|---|---|
| key | Yes | ||
| bucket | Yes | ||
| expires_s | No |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, and the description does not contradict that. It adds a useful constraint (max 604800 seconds), but does not disclose other behavioral details such as whether object existence is required or what signing credentials are needed.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence with no filler. The key constraint (expiry seconds and maximum) is immediately useful and every word earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
The output schema exists, so return values need no explanation. However, the description is thin on when to invoke this tool versus close siblings and on parameter semantics beyond expires_s. It is minimally viable but not complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description must compensate. It adds meaning for expires_s (seconds, max 604800) but leaves bucket and key entirely to their names, with no format, path, or validation details.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb ('Generate'), a specific resource ('pre-signed GET URL'), and a scope ('valid for expires_s seconds'). This clearly distinguishes the tool from siblings like get_object and presign_put.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description gives no guidance about when to use this tool instead of get_object or presign_put, nor does it mention any alternative or exclusion condition. Usage must be inferred entirely from the tool name and the sibling list.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.