Onion skin, arcs and curves

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

Annotations only declare readOnlyHint=true, and the description adds genuine behavioral detail beyond that: the output is both an image and numeric data, arcs are sampled one dot per frame, and bones default to the 3 that travel furthest when not specified. It stops short of explaining how mode/size/fps/ghosts shape the result.

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 tight sentences that front-load the three visual modes and append the important default behavior. Minor awkwardness in 'plus the numbers' and the compressed title-like opening, but nothing is padding.

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 rendering tool with 8 parameters, no output schema and zero schema descriptions, the description covers only the default bone selection. An agent still cannot tell what 'ghosts', 'size', 'fps', or the difference between 'onion', 'arcs', 'graph' and 'all' actually do.

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 8 parameters, so the description must compensate. It only explains the 'bones' default (the 3 that travel furthest) and implicitly gestures at the mode enum through prose; fps, size, ghosts, skeleton, project and animation are left with no meaning beyond their names and bare type constraints.

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 (one animation) and the concrete outputs: an onion-skin/bone-arc/value-curve image plus the underlying numbers, with 'one dot per frame' for arcs. It is clear what the tool produces, though it never uses an explicit verb like 'visualize' and does not name a sibling such as spine_render_frames to draw the boundary.

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?

There is no when-to-use or when-not-to-use guidance, and no mention of alternatives among the many rendering/measurement siblings (spine_render_frames, spine_measure, spine_compare_animations). The scope phrase 'of one animation' hints at usage but the agent must infer the selection criteria itself.

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