Remove or replace background

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

Annotations already declare non-readonly, non-destructive, open-world, non-idempotent behavior, so the safety profile is covered. The description adds genuinely useful context beyond that: the output is a transparent PNG and each call costs 1 credit, which an agent cannot get from the structured fields.

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 tight sentences, front-loading the core operation and then the prompt variant, with the cost note earning its place. No filler.

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 5-parameter image tool with no output schema, the description covers both operating modes, the output artifact, and the cost. It omits default behavior details (e.g., default engine/format) but those live in the schema, so the coverage is adequate.

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 baseline is 3. The description goes slightly beyond the schema by reinforcing the prompt/no-prompt branch semantics and giving a concrete example prompt ('on a marble kitchen counter, morning light'), which helps the agent craft the parameter correctly.

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: cutting an object out of its background to a transparent PNG, or replacing the background with a generated scene. This is clearly distinguishable from render/design siblings in substance, but no sibling is named, so the differentiation is implicit rather than explicit.

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 conditional guidance: with a prompt it generates a new scene, omit the prompt to just remove the background. That covers the two usage modes well, but there are no exclusions or named alternatives (e.g., luw_edit_image) for cases where a different tool is a better fit.

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