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

Annotations indicate not read-only and not destructive. The description adds the async generation behavior (returns generation_id and requires polling) and notes that the path is free. This is useful context beyond the annotations, though it does not cover rate limits or error cases.

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 first sentence states purpose and the primary constraint; the second covers modes and the async follow-up. All information is front-loaded and each sentence 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?

Given the tool's asynchronous nature and high schema coverage, the description provides everything needed: input constraints, mode handling, return value, and next steps. There is no output schema, so the description's mention of the returned generation_id and polling instructions is sufficient.

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?

The schema already describes each parameter (100% coverage), but the description adds the exclusivity constraint (exactly one foreground source) and the mode-specific parameter mapping (solid→color_hex, image→background_image_url). These relationships are not explicitly stated in the schema's property list, so the description adds meaningful value.

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 clearly names the operation (remove or replace an image background), the resource (Uwear's canonical free backdrop generation path), and the three modes. This is specific enough to distinguish it from all siblings, which do not cover backdrop generation.

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?

The description explicitly requires exactly one foreground source and lists the valid options. It maps each backdrop_mode to its required parameter and provides the full post-call workflow (poll get_generation_status, fetch get_generation_results), so the agent knows exactly when and how to invoke it.

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