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

Annotations already declare the safety profile (not readOnly, not destructive, idempotent), so the bar is lower, and the description still adds real information: the side effect is scoped to validation and preparation, and it deliberately does not launch translation. That boundary is not recoverable from the annotations alone. It does not say what happens if the upload was incomplete or already completed, which keeps it off a 5.

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 tight sentences with zero waste; the ordering precondition comes first and the scope limitation second. Nothing could be removed without losing a constraint.

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 only two required parameters, an output schema that covers return values, and annotations that cover idempotency and destructiveness, the description supplies the missing piece: when to call it and how far the side effect extends. Only edge-case behavior (double completion, invalid/incomplete upload) is unaddressed.

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 50%: idempotencyKey carries a strong inline description including retry semantics, while uploadId has only a pattern and length. The description adds no direct parameter meaning, though "after every byte has uploaded" implies uploadId identifies that in-progress upload. Adequate at this coverage level but no extra value.

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 action on a specific resource — validates and prepares the source media once upload is finished — and explicitly rules out one neighbouring behavior ("does not start translation"). It stops just short of naming the sibling it is not, so differentiation is by exclusion rather than by name.

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?

"Use after every byte has uploaded" is a precise activation precondition, which is exactly what an agent needs to sequence this call after the byte-transfer step. There is no statement about what to do on failure or in what order relative to translation kickoff beyond the negative clause, so it is clear context without full alternatives guidance.

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