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

Annotations already declare it read-only, idempotent, deterministic and not open-world, so the safety profile is covered. The description adds genuinely new behavioral detail by explaining what is returned (the code plus three harmonically compatible keys) and the rule behind them, which is more than the annotations convey.

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?

One front-loaded sentence with no filler. The trailing parenthetical explaining the compatibility rule is slightly dense but earns its place by clarifying the output.

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 required parameter and no output schema, the description carries the job of describing the return value, which it does (code plus three compatible keys). It stops short of stating the concrete return shape (e.g., a list of codes) but is otherwise sufficient to call correctly.

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 already enumerates accepted formats ("A minor", "Am", "F#m", "Bb major", "C", "8A"). The description adds nothing about the key parameter, so baseline 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 and resource: it yields the Camelot wheel code for a key plus the three mix-compatible keys. That is unambiguous and clearly distinct from the DJ-oriented siblings (check_mix, transpose, tempo_change), though it does not name or contrast any of them.

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?

Usage is implied by the purpose — call it when you have a musical key and want its Camelot code or compatible keys — but there is no explicit when-to-use, when-not-to-use, or pointer to a sibling such as check_mix for validating a specific pair.

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