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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so safety is covered by structure. The description adds genuine behavioral context beyond that: per-audit overage cost of $0.02 beyond the daily allowance, and the fact that hourly limits still apply. It doesn't say whether the trial status reflects live state or cached data, but the cost/limit disclosures are substantive.

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 short sentences, front-loaded with what is returned, followed by the two cost constraints. No filler, no repetition of the title or annotations, and the most decision-relevant fact (overage cost) is placed prominently.

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 is no output schema, so the description carries the burden of describing returns, and it does list the three data categories: free allowances, prices, and trial status. For a zero-parameter read tool this is close to complete; only the exact shape of the response (per-audit pricing tiers, trial expiry date format) is left unknown.

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 baseline of 4 applies. Nothing in the description conflicts with or muddies 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?

The description uses a specific verb ('Read') with a specific resource set: free allowances, prices, and the account's 7-day trial. An agent immediately knows this is an informational pricing lookup rather than a purchase action, which separates it from siblings like buy_plan or cancel_plan. It stops short of naming those siblings explicitly, so it falls just short of a 5.

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 implied rather than stated: an agent can infer this is the tool to consult before purchasing or to check remaining quota. There is no explicit 'use this when…' sentence and no named alternative for related needs such as buying a plan (buy_plan exists as a sibling). Guidance is adequate but leaves the agent to reason about the workflow.

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