Paint: read pixels

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

Annotations already declare the safe/idempotent read profile, so the description's job is reduced; it adds a cost-efficiency trait ('cheaper than a thumbnail') that the annotations do not convey. It does not describe the shape of the returned numbers, but the cost context is a meaningful addition.

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 sentences with no filler; the query modes are front-loaded and the cost trade-off is placed last as a tie-breaker. Every clause earns its place.

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 tool with full annotation coverage and a rich 5-parameter schema, the description supplies enough: it names what can be asked and the cost rationale. The absence of any note on result shape (e.g. histogram ordering tied to 'top') is the only minor gap, acceptable given 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%, so the schema already documents canvas, points, region, top and layer. The description loosely maps its query modes (points, region, histogram) to those parameters but adds no syntax or format detail beyond the schema, so the baseline of 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?

States a specific read operation ('read pixels') and enumerates the exact queries it answers: colour at points, statistics and bounding box, colour histogram of a region. This clearly separates it from the mutating siblings and from the visual-preview sibling paint_preview.

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?

Explicitly frames when to choose it over the thumbnail alternative ('Cheaper than a thumbnail when you only need numbers'), giving a clear selection criterion. It does not, however, address the other read-oriented siblings like paint_pixels or paint_pixel_grid, so guidance is strong but not exhaustive.

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