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

Annotations already declare this is a non-destructive, closed-world mutation, so the description doesn't need to restate safety. It usefully adds that the export is free, capped at 720p, and rendered client-side rather than server-side. It omits the reservation lifecycle (whether the reservation expires, and that finish_local_export must follow), which is the behavior an agent most needs.

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 no filler, with the constraint ('Widget only') placed before the action. It is efficient, though banking heavily on the reader knowing what a 'Widget' context is.

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?

This is the first step in a multi-tool flow (begin → upload/finish), has no output schema, and the description never explains the sequence or what the reservation returns to feed the next call. Combined with a mutation annotation, that leaves the agent under-informed about how to use the tool correctly end-to-end.

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?

One parameter with 100% schema description coverage, and the schema already explains that projectId comes from create_lyric_video. The description adds nothing about the parameter, which is acceptable given full schema coverage but is the baseline rather than added value.

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 ('reserve'), resource ('a free 720p export'), and location ('render in the browser'), plus a scope gate ('Widget only'). It does not name the contrasting siblings (export_video, export_hd_video) or the follow-up tool, so the differentiation is implied rather than explicit.

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?

'Widget only' gives a genuine applicability condition, which is more than most tools offer. However, it never states what to do after reserving (finish_local_export / upload_local_export) or when an agent should pick export_video or export_hd_video instead.

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