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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false. The description adds a concrete behavioral constraint beyond those — a 3MB size cap and a 'do not put zip in chat' policy — which is genuine extra value, but it never discloses what the tool returns or how putUrl/dropUrl come into existence.

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?

Two short sentences with no filler, but they are front-loaded with instructions rather than the tool's function, and the undeclared putUrl/dropUrl identifiers make the opening sentence hard to parse without prior context.

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?

With no output schema, the description must explain the return contract, and it only obliquely hints at putUrl/dropUrl without saying the tool produces them. An agent cannot tell from the definition what it will receive back or why it should call this tool at all.

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?

There are zero parameters, so per the baseline the schema carries no burden and a 4 applies. The description references putUrl and dropUrl, which are outputs rather than inputs, so it does not clarify parameters — but there are none to clarify.

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 name says upload_url and the text talks about PUT-ing to a putUrl and sending a dropUrl to a human, but it never states what the tool itself does (e.g. 'generate pre-signed upload/download URLs'). It reads as downstream instructions rather than a statement of purpose, and no sibling (claim, publish_website, render_page, etc.) is distinguished.

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 does give conditional routing advice: 'If you have the zip, PUT putUrl yourself' versus 'Only send dropUrl to the human if you have no file.' That is useful flow guidance, but it addresses what to do with the results, not when to call this tool versus its siblings.

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