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

Annotations already declare idempotent=true, destructive=false and readOnly=false; the description adds genuinely new context by stating that the source photo is unchanged and that the picture is a 512 px square cut from it, plus the auto-selection default. It stops short of describing permissions or what the response looks like.

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?

Front-loaded with the purpose, then mechanism, then crop math — a sensible order with little waste. There is a missing sentence break after 'cropped to a square' and the second sentence is dense, but nothing is superfluous.

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?

With no output schema, three parameters, and a nested crop object, the description supplies the mechanism, the default behavior, and the crop coordinate system — enough to call it correctly. It doesn't cover failure modes (photo not belonging to the artist) or confirmation of what changes on the artist record.

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 coverage is 100%, so baseline is 3; the description earns extra by explaining crop in real detail beyond the schema's one-liner — x/y as the top-left corner in fractions of the photo, size as the side relative to the photo's short side, and omission meaning centered. artist_id and photo_id get no additional semantics, so not a 5.

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 verb and resource: choose which photo is the artist's picture and how it is cropped. It also explains the underlying mechanism (the picture is a 512 px square cut from one of the artist's photos, the photo itself unchanged), which distinguishes it clearly from siblings like add_artist_photos and delete_artist_photo.

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?

Usage is implied — this is the tool to call when you want to designate an existing photo as the artist's picture — and it notes that the first photo becomes the picture automatically if none is set. But it never explicitly routes the agent to alternatives (e.g. add_artist_photos when no suitable photo exists yet) or states exclusions.

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