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

Well beyond the annotations it discloses that the video comes without a watermark, that the returned download links expire after 24 hours and must be surfaced to the user, and that each call consumes one download from the account quota — quota consumption and link expiry are nowhere in the structured fields.

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 tight sentences: what it downloads, what it returns and how to present it, then the cost and the alternative tool. Every sentence carries information and the capability statement is front-loaded.

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?

Even without an output schema, the description explains the return value (download links valid for 24 hours) and the required follow-up action (show the links to the user), plus the quota cost. Nothing an agent needs to invoke this correctly is missing.

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% and the single `url` parameter is already documented in the schema as the link copied from the app. The description adds platform examples that imply what URL forms are accepted, but nothing about format or edge cases beyond that, so the baseline 3 applies.

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?

"Baixa o vídeo (sem marca d'água) ou as fotos de um link de ..." names a specific verb (download) plus the resource (video/photos) and enumerates the accepted platforms. It clearly distinguishes itself from aplicar_marca_dagua and ver_marca_dagua by being the plain downloader.

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 routes the agent to listar_fontes to check which sources are accepted, and states the per-call cost against the account quota. It does not spell out a when-not-to-use condition (e.g., re-downloading an already-fetched link), so it stops just short of full coverage.

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