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

Annotations already declare a non-read-only, non-idempotent, non-destructive write, and the description usefully confirms what is written and where (the owner's viewing history). It does not disclose duplicate handling, whether an existing entry is overwritten, or any auth/ownership requirement — the latter being notable given the 'dono' (owner) framing.

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?

A single short sentence with the action front-loaded and no filler. It is efficient, though bordering on under-specified rather than genuinely information-dense.

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 one-parameter tool with a fully documented schema and no output schema, the description covers the core action adequately. However, the 'owner history' concept remains unexplained (whose history, under what auth, and how it relates to get_history/forget_watch), leaving a small but real gap.

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 channel_id parameter already carries its own description plus a concrete example ('GloboNews.br'). The description's 'canal assistido' merely mirrors that field, adding no format or constraint detail beyond the schema, 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?

The description gives a specific verb+resource ('Registra um canal assistido no histórico do dono' = records a watched channel in the owner's history), which is a meaningful action rather than a restatement of the name. It is distinguishable from the removal sibling forget_watch, though it never explicitly contrasts with add_favorite, which also writes channel-related state.

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?

There is no when-to-use guidance, no mention of prerequisites, and no named alternative. The agent must infer from the name alone whether this is for telemetry-style watch reporting (vs report_play) or for saving a channel (vs add_favorite).

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