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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds real value by naming the exact fields returned (amount, currency, interval, trial/setup amounts, subscription counts by state) and the underlying endpoint, which matters because no output schema exists.

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?

A single front-loaded sentence with the field list and endpoint appended; every element earns its place and nothing is redundant.

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?

With no output schema, listing the returned fields is exactly the right compensation, and pagination is fully handled by the schema. Only the absence of sibling routing guidance keeps it from being 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?

There is one parameter with 100% schema description coverage, including the 25-per-page size and the next_page chaining hint, so the schema carries the semantics. The description adds nothing about pagination, so the 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?

States a specific verb and resource ('List subscription plans') and enumerates the fields returned, with the underlying endpoint GET /plans. It is distinguishable from pinpayments_get_plan by the list-vs-get distinction, though it never explicitly contrasts with pinpayments_list_plan_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?

Usage is only implied by the 'List' verb and the plan context; the description never states when to use this versus get_plan (single plan) or list_plan_subscriptions (plans' subscriptions). Adequate but leaves routing to inference.

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