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

Annotations already declare read-only, idempotent, and non-destructive behavior, and the description reinforces this with 'Read-only; no parameters.' It adds substantial behavioral context by listing the returned JSON fields, explaining the 'doorway' concept, and noting the API key requirement. No contradiction exists.

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 dense but every clause adds information, defining important domain terms like fences, doorways, and lanes. It is somewhat compressed into a long single sentence and could be more scannable with bullets, but it stays purposeful and front-loads the core purpose well.

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 there is no output schema, the description compensates by enumerating the returned fields. It covers invocation context, read-only behavior, credential needs, use cases, and exclusions — everything an agent needs to correctly select and call the tool.

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, so the input schema carries no burden. The description explicitly confirms 'no parameters' and clarifies that the relevant context is the API key itself, which is appropriately meaningful for a parameterless tool.

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 states a specific purpose: provide a status overview of the calling API key, covering budgets, limits, volume, and recommendation. It explicitly distinguishes itself from get_usage, get_billing_status, and get_quote, making the tool's unique role clear.

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 guidance is explicit: use it first in a session and whenever a call is refused, to decide what to do next. It also names alternatives with the conditions where they should be used instead of this tool, leaving no ambiguity.

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