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

With no annotations, the description carries the full burden and explicitly self-declares 'Read-only,' which is the key safety trait, plus it discloses the monetary unit (cents) and that the draw only appears if topped up. It omits auth/account prerequisites and data freshness, but for a status read this is solid disclosure.

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 sentences, front-loaded with the 'Read-only' safety signal and the returned fields, then the usage trigger. Every clause carries information and nothing is redundant.

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?

There are no parameters and no output schema, so the description must describe the return payload itself — which it does by listing the reported fields. Minor ambiguity remains around the 'allowance window' (reset cadence/definition), but an agent has enough to call and interpret the result correctly.

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. Baseline 4 applies; no parameter-related gaps exist.

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 gives a specific verb-implied resource (billing/plan status) and enumerates exactly what is reported: plan, verified builds used, included/remaining allowance, and paid-balance draw in cents. No sibling tool covers billing, so an agent can confidently distinguish it from get_usage_guide or list_builds.

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?

It states two concrete invocation contexts: checking headroom before a large batch and diagnosing an allowance-based rejection. That is clear when-to-use guidance. It stops short of naming alternatives or stating when not to call it, so it falls short of a 5.

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