env_set_background_color

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

Annotations already declare readOnlyHint=false and destructiveHint=true, indicating a write operation. The description adds the accepted colour formats, but does not disclose other behavioral aspects like whether the previous background is overwritten or any side effects. With annotations covering the write nature, a score of 3 is appropriate; the description provides minimal extra context beyond the annotations.

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?

The description is concise, with two short sentences in Chinese and English. It front-loads the purpose and immediately specifies the accepted input formats. There is no unnecessary elaboration, making it efficient and easy to parse.

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 simple setter tool, the description covers what it does and the parameter format. The lack of an output schema is not an issue since the operation is a setter. However, the type mismatch between the schema (array) and the described accepted string format could cause confusion for an agent relying on schema validation; while the description clarifies the format, the schema itself may reject strings. This minor gap prevents a perfect score.

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 property description already states both accepted formats ([r,g,b] and '#RRGGBB'), matching the tool description verbatim. Since schema coverage is 100%, the description adds no new parameter information. The slight type inconsistency (schema says array, description says string also accepted) is present in the schema itself, so the description does not mislead; it just repeats the existing schema text. Thus, a baseline 3 is warranted.

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 states the tool sets the scene background colour, distinguishing it from sibling tools like env_set_background_map (background map) and env_set_ambient (ambient light). It specifies the exact resource (scene background) and the action (set colour), leaving no ambiguity about its purpose.

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?

While it does not explicitly name alternatives or exclusions, the purpose is self-evident among siblings (env_set_background_map, env_set_ambient, etc.). An agent can infer when to use this tool based on the task of setting a solid background colour, but there is no explicit 'use this instead of X' guidance.

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