pixel_statistics

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine domain behavior beyond that by stating results are in modality units (HU for CT) and area in mm2, but it says nothing about failure modes such as a path outside the allowed roots or an out-of-range frame index.

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?

A single sentence, front-loaded with the resource and with the output list following. Every clause (modality units, HU for CT, mm2 area) conveys information an agent would otherwise have to infer.

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?

An output schema exists, so enumerating return values was optional and it does so anyway; annotations cover the read-only profile. What remains missing is routing guidance versus the measurement and rendering siblings, but for a simple read-only statistics tool the definition is otherwise sufficient.

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%, with path, frame and the nested ROI fields all documented in the schema, so the schema carries the parameter burden. The description adds no parameter-level detail beyond the units mentioned (HU, mm2), so baseline 3 applies.

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?

Names a specific resource (pixel values within a frame/ROI) and enumerates the returned quantities (mean, std, min, max, percentiles, area), which clearly separates it from siblings such as measure_distance or render_image. It stops short of explicitly differentiating itself from those siblings by name.

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 no when-to-use guidance: it never says when to prefer this over measure_distance or render_image, nor that a roi can be omitted to analyze the whole frame. The only procedural hint ('path ... e.g. from retrieve') lives in the schema, not the description.

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