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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful behavior: asset_name falls back to the video ID when omitted, and a resource name is returned. It does not warn that because the call is non-idempotent, repeated invocations create duplicate assets, nor mention permission requirements on the customer.

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 purpose sentence is front-loaded and the Args/Returns block is compact and scannable. The docstring scaffolding is slightly formal for a three-parameter tool, but every line conveys real information.

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 simple three-parameter create call with an output schema present (so return values need no elaboration), the definition covers purpose, inputs and the default-name behavior adequately. The notable omission is lifecycle context — that the asset is inert until linked to a campaign or asset group.

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 0%, so the description carries the full burden and largely meets it: customer_id format is specified (numbers only, no hyphens), youtube_video_id is explained with a URL-extraction example, and asset_name's optional default behavior is stated. What is missing is validation guidance, such as what happens if the video ID is invalid or not owned by the account.

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 and resource ("Creates a YouTube video asset") plus the campaign context ("for use in Performance Max campaigns"), which cleanly separates it from sibling create_*_asset tools by resource type. It stops short of naming which sibling it complements (link_asset_to_campaign / link_assets_to_customer) to actually get the asset served.

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 Performance Max note implies when this tool is appropriate, but there is no explicit when-to-use/when-not or comparison to the many other create_*_asset siblings. Critically, it never says the created asset must subsequently be linked via link_asset_to_campaign or link_assets_to_customer before it has any effect.

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