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

The annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful fact beyond that — 'Free.' signals the call does not consume the monthly lookup allowance — but it says nothing about auth requirements, rate limits, or freshness of the counters.

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 short sentences, front-loaded with the returned data and ending with the quota signal. The 'Free.' fragment is abrupt but earns its place as the one non-obvious behavioral fact.

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 parameters and no output schema, the description compensates by enumerating the four values returned, so an agent knows what it will get. Only minor gaps remain, such as whose account is read in a multi-tenant context.

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 for the description to disambiguate; the baseline applies. The description does correctly indicate the scope is the whole account rather than a per-key breakdown.

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?

The description uses a specific verb ('Show') and names the exact resource and its fields: plan, monthly allowance, lookups used, and reset timing. It is clearly distinct from the sibling lookup/search tools, though it does not explicitly state that distinction.

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?

Usage is only implied: an agent can infer this is the tool to call to check remaining quota before doing lookups, reinforced by 'Free.' There is no explicit when-to-use statement, no exclusions, and no mention of the siblings by name.

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