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

Annotations declare a non-read, non-destructive write, but the description adds real behavior: it verifies stored size and is idempotent on repeat. Those traits beyond the annotations (verification step, safe re-invocation) are exactly the value-add expected here.

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?

A single dense sentence with the trigger condition front-loaded and the return/idempotency facts trailing. No wasted filler, though the return-value clause is packed tightly enough to require a careful read.

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 usefully enumerates the return values (file and attachToken for spec/result, fid for chat attachments) plus idempotency, which compensates for the missing output contract. Coverage is good for a one-param completion tool.

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 100% and there is a single documented 'fid' parameter, so the schema carries the semantics. The description adds no syntax or format detail for fid, making the baseline 3 appropriate.

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?

States a specific verb and resource ('Completes an upload via URL') and pins its place in a multi-step flow ('after a successful PUT to uploadURL'). An agent can distinguish it from the upload-initiating sibling (file_upload) via the flow role, though no sibling is named explicitly.

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?

Clear activation condition: call it only after a successful PUT to uploadURL. It also gives idempotency guidance ('Repeating it returns the same response'), reducing retry risk. No explicit when-not or named alternative, so it stops short of a 5.

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