Set or remove the video watermark

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

Annotations already declare this is a non-read-only, idempotent, non-destructive open-world mutation. The description adds real value beyond that with concrete asset constraints (square JPG/PNG, ≥150x150, ≤1 MB), which the agent cannot infer from annotations. However, it omits the confirming-call workflow and the scope of effect ('all channel videos' is stated, but no note on reversibility or quota cost).

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 front-loaded sentence with the primary action first and the removal variant second; the parenthetical constraint block is dense but earns its place. Nothing is repetitive or wasted.

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 six-parameter setter with no output schema, the description covers the core action, the removal alternative, and asset requirements, and the schema's own descriptions cover channel selection and the confirmation token. What remains missing is only secondary: offset semantics and post-call outcome.

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?

With 50% schema coverage, three parameters (image_path, offset_seconds, remove) lack schema descriptions, and the description compensates for two: it defines the image format/size limits for image_path and the meaning of remove. It says nothing about offset_seconds or the interaction between show='custom' and offset_seconds, which remain undocumented.

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 pair (set/remove) plus the exact resource: the subscribe watermark shown on all channel videos. It is clearly distinguishable from siblings like set_thumbnail or set_channel_banner, though it does not explicitly name those siblings as alternatives.

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 states the removal path ('or remove it with remove: true'), which usefully tells the agent it does not need a separate delete tool. It gives no guidance on when to choose a particular 'show' mode, which channel to target, or that a confirmation_token round-trip is required for the actual mutation.

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