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

Annotations already declare readOnlyHint=true and openWorldHint=false, but the description adds real behavior the annotations don't convey: drums are ignored, nothing is persisted ('Saves nothing'), the input is size-capped, and the result is validated against a target box. The 512 KB note roughly mirrors the schema maxLength but frames it in human-readable binary terms, which is useful.

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 tightly written sentences that front-load the core action, then add the highest-value caveats (drums ignored, no persistence). No filler and no repetition of the schema.

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 an output schema present, the description needn't explain return values, and it covers input encoding, size limits, validation scope, and the non-persistent nature of the call. The main remaining gap is what happens on validation failure and how the result should be passed downstream.

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 both parameters are documented in the schema, so the baseline is 3. The description reinforces 'base64' input and the box-validation role of the second parameter but adds no syntax, format, or default details beyond what the schema already states.

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?

The description gives a specific verb and resource: converts a base64 MIDI file into 'the melody format' and validates it against a box. It also places the tool in the workflow (so you can fit, edit and save it), which links it to siblings like fit_melody_to_box. It stops short of explicitly contrasting itself with validate_melody, which also validates melodies.

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 rather than stated: 'so you can fit, edit and save it' signals this is the first step in an import-fit-save pipeline. There is no explicit when-to-use/when-not-to-use guidance, no mention of when to prefer validate_melody on an already-imported melody, and no stated prerequisites or error conditions.

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