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

Annotations already cover read-only/idempotent safety, yet the description adds substantial behavioral depth beyond them: quota exhaustion semantics, the pack_offer top-up flow, that a key cannot purchase the top-up, that solving is unmetered on Pro/Team, and that Free accounts cannot buy packs. This is exactly the context an agent needs to reason about cost and authorization.

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?

The opening line is front-loaded with the two core facts (identity and remaining quota). The body is dense but nearly every clause addresses a distinct decision (pre-run check, failure mode, plan metering, Free constraints), so little is filler, though the paragraph is long for a no-arg getter.

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 carries the burden of explaining return values and does so field-by-field (label, scopes, tier, used/limit/reset, pack, remaining) while also covering plan-dependent behavior. An agent can act correctly without any further documentation.

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 of 4 applies; there is no parameter syntax or format the description needs to compensate for. Nothing is missing on this dimension.

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 ('who this server is acting as, and what is left this month') and enumerates precisely what is returned: API key label and scopes, account tier, per-feature used/limit/reset date, pack, and remaining. No sibling tool touches account or quota state, so it is trivially distinguishable.

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?

Explicitly prescribes the trigger condition: 'Check this before a run that will use several AI calls or Monte Carlo runs, so you can tell the user up front.' It also names the failure path (QUOTA_EXHAUSTED with pack_offer) that this tool lets the agent preempt, and clarifies Free vs Pro/Team metering differences.

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