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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the work happens on the user's device inside the app, and "this tool returns no image" — a critical fact that prevents an agent from waiting on a returned file. It stops short of describing handoff/confirmation mechanics.

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?

Purpose is front-loaded in the first sentence, followed by capability detail, then usage triggers, then an important caveat about output. Four sentences with little waste, though the compositing detail ("people standing in front stay in front") is mildly decorative.

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 one-optional-parameter, no-output-schema launcher, the description covers everything an agent needs: what it does, when to invoke it, that execution is client-side, and that no image is returned. There is no output schema to explain, and the description explicitly closes that gap.

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% and the single optional `task` parameter is fully documented in the schema with an example, so the schema does the heavy lifting. The description adds no further syntax or constraint information about the parameter, which is the baseline-3 case.

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 concrete verb and resource ("Opens Click-to-Frame, an interactive photo tool, inside the chat") and then spells out the actual capability: framing a photo region, compositing a picture into it, and cutting an object out as a transparent PNG. An agent knows exactly what this tool accomplishes without opening the schema, and there are no siblings to disambiguate against.

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?

It gives explicit trigger conditions: "Use it when the user wants to put a picture inside part of a photo, replace a painting or screen, or cut an object out." That is strong positive guidance, but there are no when-not-to-use conditions or named alternatives, so it stops short of a 5.

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