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

Annotations already cover the safe-read profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: 7-day signed URLs, a 404 when frames aren't offered, persistence of a frame across drafts while the shot is unchanged, exclusion from the video quote, and the meaning of the unavailable reasons. What's missing is any note on ordering or how frames relate to drawing one.

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?

It is front-loaded with the two things returned (frames and price) and the size is roughly proportionate to the domain. However it is a single run-on block dense with nested parentheticals, so return fields, edge cases and pricing are harder to scan than they need to be.

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 one-parameter read tool with no output schema, the description covers return fields, signing lifetime, failure mode (404), persistence semantics and the pricing caveat, which is close to everything an agent needs. The remaining gap is how this list interacts with the frame-drawing sibling and the plan resource.

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?

Only one parameter and the schema documents it at 100% coverage with a pattern and example, so the schema carries the load. The description supplies no additional information about plan_id beyond referring to "a plan's shots," which is the expected baseline for a fully-covered single parameter.

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?

The description names the resource precisely — the opening frames drawn for a plan's shots, plus the credit price of drawing one more — and defines what an opening frame is (the picture of the moment a shot opens on). The listing verb is only implicit via the title, but the object of the tool is unambiguous enough to separate it from draw_music_video_frame.

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?

"For users who want control over key shots" gives a loose motivation for calling it, and the note that frames are never part of the video's quote hints at why one would inspect before drawing. But there is no explicit when-to-use/when-not wording and no named alternative (e.g. draw_music_video_frame or get_music_video_plan) for the agent to route between.

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