Exact video frames

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

Annotations already declare readOnlyHint=true, so the safe-read profile is covered. The description does add real behavior beyond that — labelled sheet output, red change marks in diff mode, blended overlays in onion mode, and a 48-per-call cap — but says nothing about what happens when a frame number is out of range or how start/end/fps interact with explicit frame lists.

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?

One dense, front-loaded sentence with no filler; the numbering dependency and output cap are stated early. The telegraphic mode clause ('diff marks changes in red, onion blends them') is compact but slightly cryptic at first read.

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 10-parameter tool with nested objects, an unlabeled enum, and no output schema, the description is too thin — an agent cannot tell how range versus frames versus start/end combine, nor what the labelled sheet looks like. The behavioral hints are helpful but leave most of the calling surface unexplained.

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 0% across 10 parameters, including nested objects (range/crop) and an undocumented mode enum, so the description carries the full explanatory burden. It explains only the three mode names loosely and a 48-item cap — which also sits uneasily beside the schema's maxItems of 200 — while range/step, start/end, fps, crop, width, and columns get no meaning at all.

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 concrete verb and resource ('exact video frames by number') plus the deliverable ('a labelled sheet'), and ties frame numbering to spine_video_inspect so the agent knows the coordinates are shared. It doesn't explicitly separate itself from spine_render_frames or spine_motion_visual, so the sibling differentiation is implicit rather than stated.

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?

'by number (spine_video_inspect's numbering)' implies a workflow: inspect the video first, then pull specific frames — useful implied guidance. But there is no explicit when-to-use versus spine_render_frames, no statement of when diff/onion modes apply, and no exclusions.

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