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

Annotations already establish readOnly/idempotent/non-destructive, so the bar is lower, and the description still adds real behavioral detail: chord lines are transposed while lyric lines are preserved, inline bracket chords are handled, and capo suggestions are produced as a side output. It doesn't say what the return payload looks like (single string vs. structured result), which keeps it from a 5.

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 short sentences, zero waste, with the core action front-loaded and input modes and capo behavior following in priority order. Every sentence contributes new information.

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 5-parameter, single-required-param tool with no output schema, the description covers input formats, both transposition modes, and the capo side effect — enough to call it correctly. A brief note on the shape of the returned result would close the last 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; the description adds value by framing from_key/to_key and semitones as mutually exclusive input modes and by restating the three text formats in prose. It doesn't clarify spelling behavior or the first-chord fallback beyond what the schema already documents, so it is a modest gain over baseline.

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 — "Moves a song's chords to a new key" — and enumerates the three accepted input shapes (chord list, chord chart with lyrics, inline [C] chords), which makes it unmistakable against siblings like identify_chord or find_key. It does not explicitly differentiate itself from find_capo even though it also emits capo suggestions, so it stops short of 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?

"Give either from_key and to_key, or a number of semitones" is useful mode-selection guidance for invocation, but the description never says when to reach for this tool instead of find_capo (which also handles capo positions) or get_scale. Usage is implied by the purpose rather than contrasted with alternatives.

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