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

Adds critical behavioral details beyond annotations: null aiMonthlyMessages means uncapped rather than zero, weighted-token fields are always null, and the month is UTC with reset at usage.monthEndsAt. These caveats directly affect correct interpretation of the result.

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?

Three sentences, each front-loaded and useful: purpose first, then null-field interpretation, then month/reset semantics. No filler or redundancy.

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?

Given the rich annotations, zero parameters, and an output schema, the description is complete enough. It supplements structured data with the non-obvious null and reset semantics an agent needs.

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 no parameters, so the description has no parameter semantics to explain. The baseline for zero parameters is 4.

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 read operation: returns the user's plan, monthly AI limits, and current-month AI usage. The resource and scope are unambiguous, and no sibling tool overlaps this usage/limits domain.

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 purpose implies when to use it, but there is no explicit usage guidance, trigger condition, or comparison with alternatives. With no close sibling, the implied usage is adequate but not richly specified.

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