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

Annotations cover the safety profile (readOnly=false, openWorld=true, destructive=false, idempotent=false), and the description adds genuine behavior: input format and constraint (~30 s clear vocals, public https or base64), the return fields (vocal_id, duration, url), and the raw endpoint. It stops short of stating whether repeated uploads create duplicate vocal_ids, but otherwise adds real context beyond the annotations.

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 dense sentences plus an endpoint token — input spec first, then routing via vocal_id, then the disambiguating alternative. No filler; every clause 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?

No output schema exists, yet the description names the return fields (vocal_id, duration, url), so an agent knows what it gets back and how to consume it. Combined with input constraints and sibling routing, the definition is complete for this upload 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 description coverage is 100%, so both url and contentBase64 are already documented, including that base64 is 'instead of url; small files'. The description only adds the ~30 s clear-vocals guidance, which is useful but marginal against the fully-documented schema; baseline 3 is appropriate.

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 ('Upload an MP3 of a singing voice') and its scope (~30 s of clear vocals), and names the sibling it is not ('For a speaking voice use mureka_clone_voice'). An agent can immediately distinguish it from mureka_upload_reference, mureka_upload_motif, and mureka_clone_voice.

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?

Explicit down-stream routing: 'Use the vocal_id in mureka_create_song_with_lyrics, or make a reusable singer with mureka_create_character', plus a named alternative for speaking voices (mureka_clone_voice). Both when-to-use and when-to-use-something-else are covered.

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