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

Annotations flag a non-read-only, destructive call, but the description carries the meaningful economics: one credit consumed, free for previously unlocked songs, refunded on render failure. It also discloses the asynchronous contract (returns an exportId, progress and download link surface in the widget), which annotations cannot express.

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?

Four tight sentences, front-loaded with what is produced, then prerequisites/cost, then return behavior. Every sentence carries information; only the aspect-ratio restatement mildly duplicates the schema.

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?

No output schema exists, and the description compensates by explaining the exportId return and where progress/download appear. The one gap is that it does not tell the agent to poll with get_export after the render starts, leaving the follow-up step implicit.

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 enum descriptions already explain 16:9 for YouTube and 9:16 for TikTok/Reels/Shorts. The description's restatement of landscape/vertical adds only mild clarification and says nothing about projectId beyond implying the video is identified by it.

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 artifact: renders the lyric video at 1080p, watermark-free, in one of two aspect ratios. That is clearly distinguishable in substance from generic siblings like export_video, but the description never names a sibling or explains what makes this the 'HD' variant versus the others.

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 gives a real precondition (a LyricVideoGenerator account with credits, or a previously unlocked song) which tells the agent when the call will succeed. But with export_video and begin_local_export/finish_local_export in the sibling list, there is no explicit statement of when to prefer this tool over those.

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