Set or remove the YouTube branding watermark

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

Goes well beyond annotations by disclosing the critical limitation (API cannot read back a watermark) and the honesty about reporting 'accepted' rather than 'confirmed'. Also notes credit cost and connection requirement, adding behavioral context the annotations don't cover.

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 dense but every sentence contributes: purpose, timing rationale, constraints, timing options, and the API limitation. Slightly long, but the information is essential and well-ordered.

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?

Given the tool's complexity, the complete schema coverage, and no output schema, the description addresses all necessary details: how to use it, when to use it, constraints, behavior, and the lack of confirmation. Nothing an agent needs to call it correctly 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 100%, so parameters are fully documented. The description adds value by explaining image constraints (square, 150x150, 10MB), the rendering size implication, and the action default behavior when imageUrl is provided. This enriches agent understanding beyond the schema.

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 the precise verb-resource pair (set/remove branding watermark) and explains its channel-wide effect on every video, including future uploads. Clearly distinguishes from thumbnail tools and other YouTube operations.

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?

Provides clear context on when to use (before batch uploads vs. after) and explains the default full-video behavior with timingType options. Does not explicitly name alternatives or exclusions, but the usage is well implied.

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