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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is covered. The description adds one genuinely useful behavior — 'The base catalog (a2ui-atoms-v1) is always resolved' — but says nothing about ordering, completeness, or how the when-to-use metadata is shaped beyond what the output schema presumably carries.

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, no filler, with the purpose first and the base-catalog rule second. The phrase 'with a when-to-use' is slightly awkward but still compresses real information rather than padding.

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?

With no parameters, an output schema present, and annotations covering safety, the description only needs to convey scope and the base-catalog invariant, which it does. It stops just short of describing how the listed catalogs relate to the extension-catalog selection workflow.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. No parameter claims are made or needed.

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 ('List every A2UI catalog') and adds what the listing carries ('with a when-to-use'). It does not explicitly distinguish itself from the sibling get_catalog, so it falls short of a 5, but the scope ('every catalog') is unambiguous.

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 clause 'so you can pick the extension catalogs a surface needs' implies the use case (catalog selection before building a surface) but names no alternative or exclusion, and there is no explicit statement of when to call get_catalog or required_catalogs instead.

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