Set Watermark

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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the destructive overwrite is partly covered structurally; the description reinforces it with 'replacing any current one' and adds genuinely new context: viewers click the watermark to subscribe, and the quota cost of 51 units.

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?

Two short sentences, front-loaded with the core action and effect, with the quota note cleanly separated. No wasted text, though it is quite terse given the six parameters involved.

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?

An output schema exists and annotations carry the safety profile, so the description need not explain returns. It covers purpose, overwrite behavior, and quota cost, leaving little an agent needs missing before calling.

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 description coverage is 100%, so all six parameters (image constraints, start, corner, duration, from_end, my_channel) are already fully documented in the schema. The description adds no parameter-level meaning, which is the expected baseline of 3 when the schema does the heavy lifting.

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+resource and adds scope: the watermark applies to ALL videos, and setting it replaces any current one. This implicitly separates it from remove_watermark, but the sibling is not named explicitly, so it falls short of a 5.

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 phrase 'replacing any current one' implies the use case (overwrite an existing watermark), but there is no explicit when-to-use guidance or reference to the alternative tool (remove_watermark). Usage is implied rather than stated.

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