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

Annotations already declare non-read-only, non-idempotent, non-destructive, so the bar is lower, yet the description adds real value: the operation is paid from credits, max_credits must match the agreed price, and a timed-out call may already have started. That retry warning meaningfully reinforces the idempotentHint=false annotation. It does not say what happens if credits are insufficient or what the result object 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?

Dense but front-loaded: the core action comes first, then backdrop semantics, then pricing, then the retry caveat. The long parenthetical colour list is bulky but genuinely useful given the schema has no enum. No filler sentences.

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 paid, non-idempotent mutation with no output schema, the description covers cost, backdrop options, and retry safety well, but never indicates what the call returns or how the resulting image is retrieved. That leaves a real gap for an agent that must act on the result.

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%, so the description must carry the load, and it largely does: backdrop is explained as 'clear' or a #rrggbb colour with the app's palette enumerated, and max_credits is tied to prices from get_shoot or list_photos. photo_id is left implicit, which is a minor gap for a required parameter.

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: 'Cuts the person out of one of the user's photos', and clarifies the two modes (clear backdrop vs. named colour, and re-laying an existing cutout). It does not name the obvious sibling replace_background, so the agent must infer the distinction from the sibling list rather than the text.

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?

Gives clear operating context: use it on a user's photo, and on an already-cutout photo it composites onto another backdrop. It also gives a concrete retry rule ('check list_photos before calling it again'). It stops short of explicitly contrasting with replace_background or stating prerequisites such as sufficient credits.

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