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

Adds substantial context beyond the annotations: it discloses the return payload (new status plus credit notes), that it can move money, that a per-call confirmation is on by default and toggleable, and that it needs a scoped Cotlet API key. Note a mild tension with destructiveHint=false given 'cancels a customer's service', but the readOnlyHint=false is consistent with a mutation and the action is a reversible state change, so this is not a hard contradiction.

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?

Front-loads the purpose and keeps sentences information-dense, but is longer than needed and repeats the confirmation idea ('by default you confirm each call' and 'confirm with the user before each call'), which slightly dilutes the signal.

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 7-parameter mutation with no output schema, it covers return shape, auth requirements, confirmation behavior, and the key conditional parameter, so an agent has almost everything needed. It stops short of exhaustively describing interactions between cancel_option and cancel_at.

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 would be 3, but the description goes further by explaining the intent of credit_option ('how unused time on an immediate cancellation is credited') and refundable_credits_handling ('schedule_refund sends credits back at once, no_action leaves a credit note with refund due'), adding rationale the enum values alone don't convey. Minor inaccuracy: it refers to 'credit_option' where the parameter is credit_option_for_current_term_charges.

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+resource (cancel a subscription) and even the available timing modes (now, end of term, on a date), which cleanly separates it from the read/list siblings like get_subscription and list_subscriptions.

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?

Explains when each cancellation mode applies and adds a conditional prerequisite ('Contract term subscriptions need contract_term_cancel_option'), giving concrete context. It does not, however, name an alternative sibling (e.g. change_subscription_plan) or state when-not-to-cancel, so it falls short of full when/when-not guidance.

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