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

With no annotations, the description carries the full burden, and it does disclose a useful trait: compose may return diagnostics instead of Kotlin when the design is inexpressible. However, it says nothing about auth/token requirements, read-only vs mutating behavior, or what the svg/png/bundle formats return.

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 with the core action front-loaded and no filler. The middle sentence is dense but earns its place by explaining the diagnostics fallback.

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?

An output schema exists, so return values need not be spelled out, but the description only characterizes the compose path while three other formats are available. It also leaves revision semantics and token/header precedence unaddressed, so it is adequate but not complete for a four-parameter export.

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 only 50%: designId and revision are undocumented anywhere, and the description does not mention the format parameter's four options at all. Worse, its exclusive focus on compose could mislead an agent into thinking compose is the only output, so it fails to compensate for the coverage gap.

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 clear verb+resource ('Export a design') and explains what the default compose format yields. It does not distinguish itself from close siblings like ui_builder_render_native or ui_builder_validate, leaving the agent to infer the boundary.

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?

No when-to-use or when-not guidance and no named alternatives among the many render/validate siblings. The 'same gate the browser's code pane shows' line implies a use case but never states the condition that should select this tool.

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