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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world scope, so safety is covered. The description adds genuinely new behavioral context: results are scoped to the caller's token/endpoint, sizes are included, and the returned names are the resolution basis for path arguments elsewhere. It does not mention ordering or result limits, which keeps it from 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 short sentences with zero filler, and the core purpose is stated first. The second sentence earns its place by explaining what the output names are for.

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?

There are no parameters and no output schema, so the description carries little burden and it does disclose that sizes come back with each file. The one real gap is the unresolved relationship to the sibling zip_list, which an agent needs in order to route correctly between the two listing-like tools.

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?

The tool takes zero parameters, so there is nothing the description needs to disambiguate; baseline 4 applies. The description's only parameter-adjacent claim is about how the returned names are consumed by other tools, which is accurate framing for a no-arg call.

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 gives a specific verb and resource: "List the files stored for your token on this endpoint, with their sizes." It also clarifies what the returned names mean (they are the basis for every path argument). However, it never distinguishes this from the sibling zip_list, which an agent could plausibly read as the same operation.

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 sentence "These are the names every path argument here resolves against" implies this is the discovery step before path-based calls, but that inference is left to the agent. There is no explicit when-to-use, no when-not-to-use, and no mention of zip_list as the alternative.

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