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

Annotations already declare non-read-only, destructive, idempotent, and open-world behavior. The description adds value beyond them by disclosing that the job is 'metered' (cost/quota implications) and that voice handles must be plan-authorized, plus that the return is a durable operation receipt. It stops short of stating rate limits, failure/retry behavior, or why the destructive flag applies.

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?

A single front-loaded sentence with no filler; every clause (metered, plan-authorized, receipt) carries information an agent would not get from 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?

The existence of an output schema relieves the description of explaining return values, but for a 9-parameter mutation with zero schema description coverage, the definition leaves the agent without parameter meaning, cost expectations, or the follow-up polling/retrieval path. That is a substantial gap for a costly, side-effecting operation.

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 0% across 9 parameters, so the description carries the full burden and largely fails: it never mentions text length limits, speed/style/stability/similarityBoost/useSpeakerBoost tuning knobs, or language. Only voiceId and idempotencyKey are obliquely hinted at through 'plan-authorized voice handle' and 'durable operation receipt'.

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 uses a precise verb+resource ('Starts a ... text-to-speech job') and adds key scope details (metered, plan-authorized voice, returns an operation receipt). The phrase 'starts a job' clearly distinguishes it from its read-only siblings like get_tts_audio and list_tts_syntheses.

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?

No guidance on when to use this versus alternatives such as list_tts_voices (to obtain a valid voice handle) or get_job_status/get_tts_audio (to retrieve results). The mention of 'plan-authorized voice handle' implies a prerequisite but does not name the tool or condition that satisfies it.

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