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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), and the description adds value beyond them: a 200MB size ceiling, the fact that processing consumes the user's plan minutes, and that the call is asynchronous, returning immediately with a recording id. Those are exactly the operational facts annotations cannot express.

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, zero filler, and the most decision-relevant information (what it does, size limit, when to use it vs. start_upload) is front-loaded. The async/poll note closes it out efficiently.

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?

An output schema exists so return values needn't be detailed, yet the description still tells the agent it returns immediately with a recording id and to poll get_transcript — the critical control-flow fact. Combined with the quota and size limits, nothing needed to invoke it correctly is missing.

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 every one of the 11 parameters is already documented in the schema, including enum meanings and default behavior. The description only restates the URL constraint (publicly reachable, 200MB) and adds no parameter guidance beyond that, so the baseline 3 applies.

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 (downloads a media file from a URL and starts transcribing) with concrete scope (publicly reachable, up to 200MB). It explicitly distinguishes itself from start_upload for local files, so an agent can route correctly without opening either 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 an explicit trigger ("when the user shares a direct link to a media file they want transcribed"), an explicit exclusion with a named alternative ("for files on the user's device use start_upload instead"), and the follow-up step (poll get_transcript). This is the full when/when-not/next pattern.

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