Check remaining monthly units

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

Beyond the readOnly/idempotent annotations, the description discloses the zero-quota cost, that it never contacts the paid provider, and that stdio/local-dev mode returns tier 'unmetered' with no real limit. That last edge case is exactly the kind of behavioral context 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?

Purpose is front-loaded in the first sentence, followed by usage and then the return shape and cost table. The quota-cost breakdown across six sibling tools is longer than strictly necessary but genuinely load-bearing for the 'will my batch fit' use case.

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 supplies the return keys (tier, period, units_used, units_limit, units_remaining) plus the unmetered-mode caveat. That covers everything an agent needs to interpret the result and plan subsequent calls.

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 there is nothing to disambiguate and the description correctly avoids inventing parameter docs. The only nudge is that no argument behavior is described at all, which is appropriate here but leaves nothing extra to credit.

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 how much of this billing period's quota is left') and names the exact decision it supports, which cleanly separates it from the analysis siblings that actually spend quota. An agent can tell at a glance that this is the metering/inspection tool, not a data-fetching one.

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?

Explicit when-to-use cases: 'before spending any of it', answering 'how many checks do I have left', and pre-flighting a batch call to see whether it fits. It also names the alternatives by their quota cost (find_citation_leaders, analyze_citation_trend, etc.), so the agent knows when to prefer this tool over them.

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