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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely new behavior: it does not place the media on the timeline and it runs in the open editor, which is a real environment constraint. It stops short of describing return shape or limits, but it clearly exceeds the annotation baseline.

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?

Two sentences, front-loaded with what the tool produces and followed by the usage progression. Dense but every clause carries information; the parenthetical image caveat is slightly tucked away but not wasteful.

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, so the description's explanation of what is rendered (frames stamped with times) earns its place. With read-only annotations covering safety and the workflow covered, an agent has enough to invoke it correctly.

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?

At 67% schema coverage, the description clarifies the from/to pairing as a narrowing mechanism, but it never mentions 'count' or 'times', the two parameters whose semantics (how many frames, exact timestamps) are non-obvious. It partially compensates but leaves real gaps.

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 states exactly what the tool returns ('a contact sheet of a video... frames across the file, each stamped with its time') and distinguishes the image case, making it clearly separable from siblings like view_frame and view_media_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?

It prescribes a concrete workflow: look at the whole file first, then narrow with from / to, then use view_media_frame for a single moment. The alternative tool and the condition selecting it are named outright.

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