design_add_celestial

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

No annotations are supplied, so the description carries the burden, and it does add real behavioral context: the render composition (radial gradient glow, body disk, vertical shimmer band) and the note that the light path is 'on water,' implying a water-surface dependency. It stops short of stating default placement/stack order or that it is a layer mutation with undo implications.

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?

Three tight sentences, front-loaded with the core action before the rendering detail and preset list. The preset enumeration mildly duplicates the schema enum but earns its place for discovery.

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 14-parameter, output-schema-less design tool, the description covers purpose, visual behavior, and preset options adequately. It could note how the layer interacts with depth lanes or defaults, but nothing critical to a correct call is missing.

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%, so all 14 parameters are already documented, establishing the baseline of 3. The description reinforces the preset enum but adds no syntax or meaning beyond what the schema provides for azimuth, elevation, glowRadius, etc.

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 ('Add a celestial body layer (sun, moon, or star)') and enumerates the exact rendering output and presets. An agent can distinguish this from sibling atmosphere/starfield tools without opening the schema.

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?

Usage is implied by 'add a layer' semantics, but there is no explicit when-to-use guidance, no mention of prerequisites, and no routing against closely related siblings like design_add_starfield or design_add_sky. The alternatives are left to inference.

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