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

Goes well beyond the readOnlyHint=true / openWorldHint=false annotations: duration cap (5 minutes), daily quota (20/60 audios, "the same melody again is free"), PRO-only gating for music_box, and the inheritance rule that saved songs use the author's chosen sound unless overridden. This is unusually rich operational context for a render tool.

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?

Front-loaded with the core action and the input fork, then packs constraints and sound rules efficiently. Dense and mostly waste-free, though the quota/account clauses crowd the final sentence and could be slightly tighter.

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, return values need not be described, and the description covers the key behavioral facts (input modes, sounds, quotas, duration). Only minor gaps remain, such as not clarifying what the returned audio handle looks like or its lifetime.

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 71%, so most parameters are self-documented, but the description adds real meaning the schema lacks: it explains the synth-vs-music_box tradeoff (free vs PRO), when song_id vs a melody object is required, and the sound override semantics. It leaves illegal_threshold_ticks and claim_token to the schema, which is acceptable.

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+resource ("Creates an MP3 of a melody... or of a saved song") and explicitly frames it as the listening/rendering path via "before or without saving it," which cleanly separates it from create_song. An agent can distinguish it from export_song and create_song without opening any schema.

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?

Clearly states the two input modes ("Pass either song_id or a melody (box, bpm, notes)") and the intent (so you and the person can hear it). It gives conditions but does not name any sibling as an alternative or an explicit when-not-to-use case.

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