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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond them by disclosing the return payload (transcript, confidence, language, duration, word and speaker counts, per-utterance speaker/timing) and the billing model (3 credits, charged only on success). The only-succeeds-billing detail is genuinely decision-relevant information absent from structured fields.

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 sentences, front-loaded with the capability, followed by output shape and then cost/alternatives. No filler, and each sentence supplies a distinct decision input.

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 correctly assumes the burden of describing return values, and it also covers cost and sibling routing. Nothing an agent needs to select or invoke this tool is left unexplained.

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 the baseline is 3 and the schema already documents audio_url, language, and speaker_labels. The description mentions diarization and timestamps conceptually but adds no syntax, defaults, or format detail beyond what the schema carries.

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 and resource ('Transcribe audio') plus the differentiating capability (speaker diarization and timestamps). It explicitly distinguishes itself from the nearby siblings stt and subtitle, so an agent can route correctly 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?

Names concrete scenarios (meetings, interviews, podcasts 'where who spoke when matters') and gives explicit alternatives with their selecting conditions: stt for short-clip word timings, subtitle for caption files. This is textbook when/when-not/alternative guidance.

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