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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral fact — top-ups are out of scope and happen in the browser — but says nothing about pagination behavior for the ledger, whether the estimate call is a pure calculation, or what the response contains.

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 short sentences with no filler and the resource list front-loaded. The telegraphic noun-pile style is efficient but slightly hurts readability versus a verb-led sentence.

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?

Read-only with no output schema lowers the return-value burden, but a 4-parameter tool with a nested object at 0% schema coverage needs more than a comma-separated feature list. The undefined 'AWT' term and the unexplained estimate/paging parameters leave real gaps before an agent can call it 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?

Schema description coverage is 0% across 4 parameters, including a nested 'estimate' object with three sub-fields, so the description carries the full burden. 'Creative cost quotes' faintly implies the estimate parameter and 'credit ledger' implies paging, but model/variations/duration_seconds and the meaning of limit/cursor are left completely unexplained.

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 lists the resources returned (AWT balance, credit ledger, plan and renewal, platform fees, cost quotes), which does differentiate it from siblings like payments_get or subscriptions_list. But it is a bare noun list with no verb, and 'AWT' is an unexplained acronym, so an agent must infer that this is a read operation from the name and annotations rather than the prose.

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?

'Top-ups stay in the browser' is a partial exclusion — it tells the agent this tool cannot top up — but there is no positive when-to-use framing and no routing against other billing-adjacent siblings (payments_get, checkout_get, subscriptions_list, stripe_checkout_purchases_get).

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