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

The annotations already declare readOnlyHint=true, and the description is consistent with that by saying 'List' and GET. It adds useful behavioral detail beyond the annotation: the operation supports filtering, ordering, and cursor pagination, and identifies the exact Keap endpoint. It does not disclose response shape or rate limits, but for a read-only list operation these omissions are minor.

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 short sentences: the first defines the action and resource, the second summarizes capabilities, and the third gives the endpoint. It is front-loaded, with no filler or repetition of the title beyond the core purpose.

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 read-only list tool with no required parameters and full schema coverage, the description is nearly complete. It conveys the resource, pagination model, and endpoint. It does not explicitly describe the response format or next_page_token semantics, but these are largely implied by 'cursor pagination' and are absent from the 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?

The schema already documents all four optional parameters at 100% coverage, so the baseline is 3. The description's mention of filtering, ordering, and cursor pagination summarizes the parameter capabilities but adds no new syntax, constraints, or examples beyond what the schema provides.

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 states a specific action ('List') and resource ('recurring subscriptions / payment plans'), and names the underlying endpoint (GET /subscriptions). This makes the tool's function unambiguous and implicitly distinguishes it from sibling list tools for orders, contacts, products, etc.

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?

The intended use is implied by the resource name ('subscriptions') and the list action, but the description does not explicitly state when to use this tool versus sibling list_* tools or when not to use it. There are no exclusionary conditions or alternative tool pointers.

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