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

Goes well beyond the annotations (which only declare non-read-only, non-idempotent, open-world, non-destructive): it discloses the return shape ('one complete song with only that stretch replaced, on the source song's model'), a hard cost/plan gate ('needs a paid Mureka plan, 20 Gold'), and the asynchronous job contract ('the song or a jobid for mureka_get_job'). These are exactly the behavioral traits an agent must know before calling.

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?

Dense and front-loaded: the core operation leads, then constraints, then sibling routing, then the endpoint. Every clause earns its place, though the telegraphic fragments ('A job: the song or a jobid for mureka_get_job. POST /music/edit.') are terse enough to slightly hurt readability.

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 6-parameter mutation tool with no output schema, the description supplies the missing pieces: cost, plan requirement, what is and is not replaced, the return artefact, and the async job handoff. Nothing an agent needs to invoke it correctly is absent.

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%, so start_milliseconds, end_milliseconds, keep_melody, lyrics and song_id are already fully documented in the schema. The description reinforces the time-range framing and the keep_melody default but adds no syntax, units or edge-case meaning beyond what the schema provides. Baseline 3 applies when the schema carries the load.

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 precise verb+resource+scope: 'Re-sing one time range of a song (start_milliseconds to end_milliseconds) with new lyrics and keep the rest.' It also names the sibling operations it supersedes for adjacent tasks, so an agent can distinguish it from mureka_extend_song and mureka_remix_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?

Explicitly routes two near-siblings: 'To add to the end use mureka_extend_song, to restyle the whole song mureka_remix_song.' The when/when-not conditions are stated inline, and the async-job follow-up (mureka_get_job) is named, leaving nothing to inference.

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