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

Annotations only carry readOnly/destructive/openWorld hints, but the description adds substantial context beyond them: refunds are irreversible, multiple partial refunds are allowed up to the transaction total, the note stays internal, the subscription is untouched, confirmation defaults on, and an API key requirement. This is genuinely rich behavioral 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?

Content is front-loaded and useful, but it repeats itself: 'Does not cancel the subscription' and 'It does not cancel the subscription' say the same thing twice, and 'full or partial'/'in full or in part' is duplicated. Tightening would improve it.

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?

For a 3-param mutation tool with no output schema, the description covers prerequisites, side effects, alternatives, and failure modes well. Only minor gaps (e.g., what a successful refund returns) remain, which is acceptable given no output schema.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning: the note is internal-only and the partial-amount constraint ('up to the transaction total and never more') clarifies how 'amount' behaves beyond the schema's terse default text.

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 verb and resource (refund a transaction) with precise scope: full or partial, one payment or rebill. It explicitly distinguishes itself from cancel_subscription, so an agent can route between them without opening either schema.

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?

Explicitly tells the agent when to use this and what to do alongside it ('call cancel_subscription too'), plus a concrete failure condition (PayPal balance too low). The 'reaches other people: confirm before each call' guidance is direct usage instruction.

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