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

Annotations already declare readOnlyHint=true and openWorldHint=false; the description reinforces this with the explicit "Saves nothing" side-effect statement and adds output behavior ("Every issue names the note and how to fix it"). It goes beyond the annotations by describing the diagnostic content of results, though it says nothing about failure semantics for malformed input.

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, front-loaded with the core purpose, then output format, then the workflow instruction. No filler and every sentence earns its place.

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 explained, and the description still summarizes the error-shape (issues with note and fix). Purpose, checks, side effects, and call timing are all covered for a read-only validation tool.

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 description maps behavior back to specific parameters: "off-grid notes" explains snap_beats, "same note repeated too fast" explains illegal_threshold_ticks, and "tempo and length" covers bpm. It adds conceptual meaning rather than merely restating field names.

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 ("Checks whether") and resource ("a melody... on a music box") and enumerates the actual check categories (out-of-box notes, repeats too fast, off-grid, tempo, length). An agent can immediately tell this validates rather than creates or renders, distinct from most siblings.

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?

Gives an explicit workflow trigger: "Call it before offering a melody to the person." That is clear when-to-use guidance. It does not, however, name the sibling alternative fit_melody_to_box or state when validation is unnecessary, so it stops short of full routing guidance.

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