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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and scope are covered. The description adds meaningful context beyond that: the counters are scoped to 'this API key' and reported over two windows (today, this hour). It does not disclose return format, reset timing, or whether limits are plan-based.

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?

One sentence, front-loaded with the resource and the two time windows, with no padding. Minor awkwardness in the phrasing 'has used and has left' slightly hurts readability but nothing is superfluous.

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?

For a no-parameter, no-output-schema read tool this is nearly sufficient: the description tells the agent exactly what the response conveys (used and remaining checks, per day and per hour). What is missing is whether 'left' is a hard quota and what happens at zero, which would matter for deciding to call run_checks.

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 no parameter meaning to add and the schema already forbids additional properties. Baseline 4 applies; the description correctly does not waste words on nonexistent inputs.

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 names the resource (API key usage) and the specific quantities returned: checks used and checks remaining, for both the day and the hour. That is clear enough to separate it from siblings like list_checks and run_checks, though it lacks an explicit verb (e.g. 'Get/read') and never restates the tool's identity beyond the counters.

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 quota-check tool to call before run_checks, but the description never says when to use it, when not to, or that it is the alternative to running a check blind. No prerequisites or quota-exhaustion behavior are mentioned.

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