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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered. The description adds no behavioral context of its own — no note on result ordering, pagination limits beyond the schema, inclusion of canceled subscriptions, or external API failure behavior.

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 endpoint is front-loaded. But the brevity comes from under-specification rather than economy — there is essentially no informational content to compress.

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 simple read-only, two-parameter list endpoint with full schema coverage and complete annotations, the bare minimum is arguably met. Still, the description never states what the call returns or whether the plan must exist/be active, leaving an agent to rely entirely on structured fields.

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 100% and both parameters (plan_token, page) are documented in-schema, including page size and the next_page chaining hint. The description adds no meaning beyond the schema; baseline 3 applies.

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 identifies the resource and narrows it to one plan ("Subscriptions to one plan"), implicitly distinguishing it from pinpayments_list_subscriptions and pinpayments_list_customer_subscriptions. However, it is a noun fragment with no verb (list/fetch) and adds nothing beyond the title and the raw endpoint path, so an agent has to infer the action.

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?

There is no statement of when to use this instead of the near-identical siblings pinpayments_list_subscriptions or pinpayments_list_customer_subscriptions, and no prerequisites. The only hint is the phrase "to one plan," which implies the plan_token is the selector, but no explicit routing guidance is given.

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