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

Annotations already declare non-read-only, non-idempotent, non-destructive, open-world behavior. The description adds genuine scope context, that this is a static composition with no image generation and that indicators/functional widgets stay independent, plus the cost signal "free." It omits permission/ownership requirements and what happens on repeat calls.

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?

A single dense sentence front-loads the operation and its key constraint. Efficient, though the semicolon-joined clauses make it slightly harder to parse than two short sentences would.

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 five-required-parameter creation tool with 20% schema coverage and no output schema, the description leaves major gaps: how children are laid out or ordered, whether overlaps are valid, ownership/permission prerequisites, and the consequences of composition. It states what the tool is not (image generation) better than what it requires.

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 only 20% (packId and componentId only; name, width, height, children, and bounds are undocumented). The description's "existing icon/frame revisions" lightly hints at what children reference, but it adds no meaning for the 8-item child limit, bounding rules, or dimension constraints.

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 ("Create a free static composition") and constrains the input to "existing icon/frame revisions" with "No new image generation." That implicitly separates it from generative siblings such as generate_ui_pack, though no sibling is named outright.

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 rather than stated: compose from existing revisions, and don't use this when new imagery is required. There is no explicit when-to-use/when-not framing and no named alternative (e.g., generate_ui_pack) to route an agent toward.

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