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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered. The description adds what the payload contains, but since an output schema exists that content is largely restated rather than new behavioral insight; nothing about caching, rate limits, or failure modes (e.g. unknown slug) is disclosed.

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: payload summary first, then the when-to-use cue, then a copyable example. No filler and the most decision-relevant information leads.

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?

A read-only, single-lookup tool with 100% schema coverage and an output schema — the description covers purpose, contents and a sample call, which is sufficient. It lacks any error behavior for an invalid or unknown slug, a minor remaining gap.

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 baseline is 3, but the inline example {"slug": "empty-state", "limit": 8} demonstrates realistic values and pairing beyond the schema's own prose. That concrete call sample is the added value.

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+resource ('One UI pattern') and enumerates the payload scope: definition, best examples, related patterns, technologies. That is far more informative than the title and lets an agent distinguish it from list_patterns. It stops short of naming sibling tools explicitly, so it is a 4 rather than a 5.

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?

'Use it before designing that pattern' is an implied usage cue, not a routing rule. It never contrasts with list_patterns (discovery) or related_resources (graph traversal), so an agent must infer which sibling fits which situation.

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