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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds return-shape detail (definitions side by side) and a conditional behavior ('plus the catalog's written comparison when one exists'), which is context not present in the structured fields.

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, front-loaded with purpose and scope, followed by the return behavior. The example list is dense but each item adds disambiguation value; no filler or repetition.

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 one fully documented parameter and no output schema, the description covers both input acceptance and what comes back. It does not mention behavior when a supplied pattern is unknown or unmatched, a minor gap for a single-parameter lookup tool.

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 100% and the single parameter's schema entry already documents the 2-4 ids/names/short-descriptions format with examples. The description largely restates that ('Accepts ids, names or short descriptions') without adding new syntax or constraint detail, so the baseline of 3 applies.

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 (compares/diff) and resource (UI patterns) with a precise scope of 2 to 4 items, plus four concrete example pairs. An agent can immediately tell this is a multi-pattern diff rather than a single-pattern lookup, though no sibling tool is named explicitly.

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 phrase 'easily confused UI patterns' and the vs-style examples imply when this tool is appropriate (disambiguating confusable patterns), but there is no explicit when-to-use statement, no when-not-to-use, and no named alternative such as get_ui_pattern.

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