Check usage

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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds useful behavioral context by specifying what the check returns (plan tier, usage counters, reset date) and explicitly confirming it takes no arguments, without contradicting the annotations.

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 description is a single well-structured sentence that front-loads the purpose, lists the returned values, and ends with the no-argument note. Every part earns its place with no wasted words.

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 simple zero-argument, read-only usage query with no output schema, the description supplies the needed return-value details and relies on annotations for the safety profile. No important calling information is missing.

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 has zero parameters and the schema coverage is effectively complete, so the baseline is 4. The description reinforces this with 'Takes no arguments,' though it adds no additional parameter meaning beyond the empty schema.

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 ('Check') and resource ('Lyrenth credit usage'), and enumerates the exact data returned: plan tier, credits used, credits remaining, and reset date. This clearly distinguishes it from sibling tools that read URLs.

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?

The description makes the intended use obvious by naming the resource and key output fields, and the sibling tools are unrelated URL readers. It does not explicitly state when not to use it or name alternatives, but no exclusion is needed given the context.

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