sprite_measure

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

No annotations are provided, so the description carries the behavioral burden. It does add useful context: measurements are per-frame, canon regions affect which rows are returned, and row positions can vary across frames. However, it does not explicitly state whether the tool mutates anything, how it handles missing canon files, or what the return format is. 'Measure' implies read-only behavior, but the description leaves some behavioral details implicit.

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?

The description is a bit longer than the minimum, but each sentence earns its place: the first lists what is measured, the second gives the intended timing, and the third grounds the guidance in a concrete failure mode. It is front-loaded and readable, though the bug anecdote could be trimmed without losing core meaning.

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 measurement tool with no output schema and no annotations, the description covers the key outputs, the per-frame nature, and the role of canon regions. The input schema handles the parameter semantics. It stops short of describing the exact return structure or edge-case behavior, but it gives an agent enough to invoke the tool correctly and interpret its results.

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%, so the schema already documents all four parameters. The description adds conceptual context around canon regions, which relates to canonPath, but it does not give additional parameter-level detail beyond the schema. Per the rubric, baseline 3 is appropriate here.

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 opens with a specific verb and resource: 'Measure a sprite's anatomy per frame and its cross-frame jitter.' It enumerates concrete outputs (bounding box, top row, widest row, cap width, waist row, region first rows), which makes the tool's purpose unmistakable. This clearly distinguishes it from siblings like sprite_verify or sprite_repaint, which do not measure anatomy.

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 description gives an explicit use case: 'Use before placing anything relative to a sprite: measured rows beat guessed proportions.' It also provides a concrete bug example showing when this tool prevents errors. It does not name alternative tools or state when not to use it, but the context is strong enough for an agent to route correctly.

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