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

Annotations already establish readOnly, idempotent, closed-world, and non-destructive behavior, so the bar is low. The description adds useful semantics: the result is implicitly scoped to the authenticated user with no identifying input, and it names the data categories returned. It doesn't mention freshness/caching, but that's minor.

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?

Two sentences, front-loaded with what is returned and followed by when to call it. No filler or redundancy.

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 an output schema documenting the return shape, rich annotations, and no parameters, the description covers everything an agent needs: what it returns, who it applies to, and when to invoke it.

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?

Zero parameters, so the baseline is 4. The description reinforces this by framing the result as the signed-in user's account, making it clear no identity parameter is needed.

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 (Returns) plus the exact resource: the signed-in user's plan, transcription minutes used/remaining, and service capabilities. It is clearly distinguishable from all siblings, which operate on transcripts, uploads, and translations.

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 concrete call triggers — before large transcription jobs, or when the user asks about plan, usage, limits, or capabilities. It stops short of an explicit exclusion or a named alternative, but no sibling tool overlaps this function, so the guidance is effectively complete.

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