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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds that it returns 'current' facet values and a total count, but doesn't describe output format or freshness semantics. With annotations doing the heavy lifting, this is adequate but not rich.

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?

Front-loaded with the enumerated facets, followed by the usage hint. The Korean translation in parentheses is redundant for most agents and adds length without new information, slightly hurting conciseness.

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 zero-param, read-only, idempotent facet listing, the description covers what it returns well enough. No output schema exists, so it correctly names the returned fields (genres, keys, vocal types, languages, count), leaving little ambiguity.

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?

Zero parameters, so baseline is 4. The description correctly implies this is a no-argument catalog enumeration, matching the empty schema with no discrepancy.

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 (List) and enumerates the exact resources (genres, musical keys, vocal types, languages, total song count). This clearly distinguishes it from siblings like search_songs and get_song, which return songs rather than facet metadata.

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?

Explicitly says it is 'Useful before calling search_songs,' giving a clear usage context and naming the alternative workflow. It doesn't state when NOT to use it, but the pre-search framing is strong guidance.

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