Generate a time-limited presigned URL for an object

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

Annotations already mark this as non-read-only and destructive, and the description adds meaningful context: credentials are not exposed, the URL is time-limited, and put exports a write capability outside the MCP boundary requiring confirmation. No contradiction with annotations.

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?

Three sentences, front-loaded with the core function, followed by use cases and a safety caveat. Every sentence earns its place with no filler or redundancy.

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?

Given the rich schema descriptions and annotations, the description covers purpose, usage context, and the key safety caveat. It does not describe the return value shape, but the URL output is implied and no output schema exists, so this is acceptable.

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 coverage is 100%, so the schema already documents all 7 parameters. The description adds some cross-parameter context (operation='put' requires confirm=true), but this is also stated in the schema, so the added semantic value is minimal.

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 uses a specific verb ('Generate') and resource ('presigned URL for one object'), clearly states GET/PUT access and time-limitation, and distinguishes itself from sibling inline-transfer tools by mentioning 'content too large for scaleway_s3_get_object/put_object's inline transfer.'

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?

It explicitly says when to use this tool: handing a download/upload link outside MCP or for content too large for inline transfer. It also names the alternative tools and gives operational guidance that operation='put' requires confirm=true.

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