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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond the annotations: the quota cost ('Custa 1 unidade da cota') and the semantic restriction that only comment-capable channels are listed. No contradiction with annotations.

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?

The description is short and each sentence earns its place: it states the object, the output shape, the usage timing, and the quota cost. The most decision-relevant information is front-loaded, and there is no filler or repetition of schema data.

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?

For a read-only list tool with a single optional parameter and no output schema, the description covers what is listed, when to use it, and cost. The only notable gap is the unexplained 'account' parameter, which prevents the description from being fully complete for a caller who wants to be selective about which account's channels to list.

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?

There is exactly one parameter, 'account', and the schema describes its properties but has 0% schema description coverage. The description never mentions 'account', so the agent cannot tell what the parameter means, whether it is genuinely optional despite the schema, or how it affects which channels can be returned. With low coverage, the description is responsible for compensating, but it does not.

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 uses a specific verb and resource: 'Lista os canais do YouTube conectados', and adds the distinctive scope 'os que podem responder e moderar comentários'. It enumerates the included fields (id, nome e estatísticas), which makes the tool easy to tell apart from broader channel, search and feed tools among the siblings.

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 description gives an explicit instruction on when to call the tool: 'Use antes de responder para confirmar de qual canal a resposta vai sair'. It does not name explicit alternatives or exclusions, but the context where this should be invoked is clear enough to place it before commenting-related actions.

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