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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered and the description need not repeat it. What the description adds is content scope — notably that internal levels are reported both now and in past versions, and that servers/community tags are included. It says nothing about behavior on a miss (unknown song, ambiguous title) or about response volume, which would be the genuinely valuable additions here.

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 the resource and the returned fields, then the filtering scope. No filler or hedging. It is dense with Japanese terms and parenthetical glosses, which is justified for domain naming but makes it slightly harder to scan than a plainer phrasing 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?

An output schema exists, so return values need not be described, and the description nonetheless summarizes the payload well; annotations cover safety, and the schema fully documents all five parameters. The remaining gap is workflow placement — nothing tells the agent this is typically called with an ID obtained from search_songs (that hint appears only inside the schema).

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 every parameter carries enum values or a precise description, so the schema does the heavy lifting; baseline 3 applies. The description's 'filter by type, difficulty and server' merely restates the schema's parameter names and adds no syntax, defaulting, or interaction details beyond it. The nuance that a server filter yields that server's own level where it differs lives in the schema, not the description.

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 concrete verb-and-resource pair: returns details of a maimai DX song and its charts, and enumerates the specific data returned (level, internal level across versions, note counts, designer, release date, servers, tags). That is far more specific than the title alone. It does not explicitly distinguish itself from the sibling search_songs, so an agent must infer that this is the detail/lookup tool versus the discovery tool.

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 closing sentence 'Filter by type, difficulty and server' implies the narrowing use case for the optional parameters, which is useful context. However, there is no explicit when-to-use statement, no mention that this is the follow-up call after search_songs, and no guidance on when to prefer or avoid it over the sibling calculate_* tools.

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