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

Annotations already cover read-only safety, but the description adds substantial context beyond them: it defines exactly what `remaining` means (account balance narrowed by the key's monthly cap, 'never a second rule'), what `used` counts (finished videos plus minutes held for in-flight renders), and that `limit` = used + remaining. It also discloses the downstream 402 quota_exceeded failure mode, which is real behavioral information an agent cannot get from the annotation set.

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 actionable directive before the semantics, and every clause about the counters earns its place. Minor redundancy: the 'before approve_lesson' instruction appears twice (once parenthetically, once in the use-when sentence), and the backtick/semicolon density makes it slower to scan than necessary.

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?

There is no output schema, so the description carries the burden of explaining the response — and it does, defining all three counters and how they relate. Combined with the 402 escalation path, an agent has everything needed to call this and interpret the result.

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?

The tool takes zero parameters, so the baseline is 4. The description instead spends its effort documenting the return semantics (`remaining`, `used`, `limit`), which is the right trade-off given there is no input to explain.

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 ('Check remaining video minutes') and immediately scopes it against the sibling that consumes the result ('call this before approve_lesson'). An agent can distinguish this from list_lessons or get_lesson 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?

Gives an explicit when-to-use rule ('when the user asks how much is left, or before approve_lesson when the balance may be tight') plus the consequence of skipping it ('approve_lesson answers 402 quota_exceeded when the lesson does not fit'). The alternative and its selection condition are both named.

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