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

Annotations already declare it is a non-readonly, non-idempotent, open-world write. The description adds latency expectations (10s to 1 min), the synchronous-vs-async return contract, and per-account rate limits (1/day free, unlimited Premium) – exactly the context annotations cannot convey.

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?

Front-loads the core action, then the pattern glossary, then the async/quota rules. Dense but every clause carries information; only slight cost is the parenthetical per-pattern asides that lengthen the block.

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?

No output schema exists, yet the description fully specifies return values (MP4 link or an id for polling), the polling sibling, latency, and quota. Nothing an agent needs to call it and handle the result 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 78% with 6 enums, so structured fields carry most weight. The description goes further by explaining what each padrao actually does (letreiro crosses the screen, quicando bounces, etc.), which meaningfully exceeds the bare enum labels. cor, estilo, tamanho and opacidade remain unelaborated but are partially self-documenting.

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 (download the video and apply a TEXT watermark) and explicitly scopes the source to the same sites as baixar_midia, distinguishing it from that sibling. An agent can tell immediately what this produces.

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?

Explains the async flow (if not ready, call ver_marca_dagua with the returned id), the free/Premium quota, and instructs to ask the user for the text if missing. It does not contrast against other siblings beyond baixar_midia, but the operational guidance is clear and actionable.

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