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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds the economics the annotations cannot express: one purchased credit per call, no free trial, and the precise idempotency contract that retrying the same preparedRequestId returns the same job without charging again. The timeout guidance and PAYMENT_REQUIRED branch are exactly the kind of failure-mode context an agent needs before a destructive, credit-spending call.

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 action and the cost, then the failure branches. Nearly every sentence is an actionable rule, though 'No free audio trial' partially restates 'Spends ONE purchased song credit' and could be folded in.

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 no output schema, the description still conveys that the call returns promptly with a job that get_song_job can be polled, but it never states the returned shape (e.g. a job id) explicitly, leaving the agent to infer it from the retry sentence.

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 0%, so the description must carry the parameter, and it does explain the important semantic: preparedRequestId is an idempotency key whose reuse is safe. It never says where that ID comes from (presumably prepare_song), which leaves a small gap for an agent that doesn't already hold one.

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 (start) and resource (the prepared song) and scopes it to 'after the user has asked to generate it', which cleanly separates it from prepare_song (which only prepares) and get_song_job (which polls). An agent can pick it apart from all six siblings without opening a 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?

Gives explicit preconditions (user must have asked to generate), an explicit alternative for the PAYMENT_REQUIRED case (create_checkout_link, and only after the user chooses), a follow-up route (get_song_job after 15 seconds), and an explicit prohibition (never re-create a request because of a timeout).

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