Get one full-resolution frame

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds useful operational traits: the 2000 px long-edge output bound and the fact that crop enlarges a region rather than changing which frame is returned. It stops short of stating the return type (image vs. path/URL) or any failure behavior for bad paths, so it is not a 5.

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 short sentences with zero filler; the core purpose and resolution bound come first, followed by the crop tip. Every sentence earns its place and nothing is repeated from the name or title.

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 read-only extraction tool with full schema coverage and annotations covering the safety profile, the description is close to complete: purpose, resolution cap, and the crop enlargement trick are all present. The remaining gap is that it never says whether it returns an image payload or a path/reference to one, which matters because there is no output schema.

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 100%; every parameter, including the nested crop fields with a worked example, is already documented in the schema. The description's only parameter-adjacent contribution is 'Pass crop to enlarge a region', which restates rather than extends the schema's meaning. Baseline 3 applies when the schema carries this much detail.

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 a specific verb and resource: it returns one still frame at full resolution, with a concrete resolution bound (long edge up to 2000 px). It is clear what the tool does, but it never names the sibling 'zoom' or explains how this differs from zooming via that tool, even though 'Pass crop to enlarge a region' overlaps with what 'zoom' likely does.

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 intended use is stated clearly enough: read small on-screen text or inspect details. However, there is no explicit when-not guidance and no routing to alternatives, even though 'zoom', 'watch_video', and 'transcribe' sit alongside it; an agent must infer that crop enlargement here competes with 'zoom'.

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