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

Adds real context beyond annotations: it blocks up to wait_seconds, surfaces status/job_id values, and discloses an auth carve-out ('No token needed for the first free files'). Given readOnlyHint=false and idempotentHint=false, it could have gone further on cost/quota implications of tier='fast' and on repeat-call behavior, which is the remaining gap.

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 outcome, then branches, then the wait/auth caveat — no wasted preamble. The parenthetical '(open folders with list_files)' is slightly intrusive but carries usable routing information.

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 six parameters, a full schema, and an output schema already defining return shapes, the description supplies exactly the missing piece: the state machine (pick_required → share_id/file_id, running → get_job) and the auth caveat. Nothing needed to invoke it correctly is absent.

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 baseline is 3; the description earns above that by describing the pairing relationship the schema cannot express — share_id and file_id must be supplied together, drawn from a prior pick_required answer, with folders opened via list_files. The tier parameter's free/fast trade-off is still not explained anywhere.

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 ('Fetch a link and return a download URL') plus the compound-call value proposition ('in one call'). It also names the exact follow-up siblings (list_files, get_job, get_download_link) so an agent can place it in the flow rather than confusing it with a raw link checker.

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?

Gives explicit conditional guidance for the two non-happy paths: status 'pick_required' → re-call with share_id + file_id, and status 'running' → get_job then get_download_link. It does not, however, say when to prefer this over the sibling start_download or check_link, so the entry-point choice is left to inference.

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