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

With readOnlyHint=true already declaring the safe-read profile, the description still contributes useful behavior: the returned field set, the meaning of the halted status, and that paging is driven by next_page from the prior reply. No rate limits or ordering guarantees are given, so not a 5.

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 tight sentences: what it returns, how to filter, the halted tip, pagination. Zero filler and the resource scope is front-loaded.

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?

Eleven optional parameters with no output schema, so describing the returned fields and pagination behavior carries real weight and is done well. Minor gap: sort_by/sort_key and the created_at/updated_at bounds are only in the schema, though coverage there is complete.

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 baseline is 3; the description goes beyond by explaining the operational intent of status=halted and by tying pagination to next_page, rather than merely restating parameter names.

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 ("List the store's subscriptions") and enumerates the payload contents (status values, subscriber, plan policies, line items, next_billing_at). An agent can distinguish it from recurpay_get_subscription (single) and recurpay_list_order_subscriptions (order-scoped) without opening a 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?

"Use status=halted to find subscriptions whose renewal payment failed" gives a concrete diagnostic recipe, and the filter sentence names the primary narrowing axes. It stops short of naming alternatives or when-not-to-use guidance, so it stays below a 5.

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