getUserSubscriptions

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds the WHMCS billing backing and, unlike a bare read tool, fully describes the actual response payload (nested `message` object, `subscriptions` array, and field meanings like `domainstatus` values). It stops short of error behavior, pagination, or rate-limit context, so it does not reach 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?

Long but deliberately structured with bold section labels and front-loaded purpose; each block (Required, Use when, See also, Returns) earns its place by answering a distinct invocation question. No filler or repetition despite the length.

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, the description supplies the full return contract including the non-obvious nested `message` shape; annotations cover the safety profile; both parameters and their selection rule are documented; and the sibling landscape is mapped. Nothing an agent needs to call this correctly is missing.

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%, yet the description still adds substantial semantics: it identifies user_id as the standard BD member ID and client_id as the WHMCS billing record ID stored as `users_data.clientid`, explains why to prefer user_id, and warns that exactly one must be passed (the schema itself marks nothing as required). This meaningfully exceeds the schema text.

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 ('Get member subscriptions - Fetch the subscription / membership-plan history for a specific member') and explicitly distinguishes itself from the nearest siblings by naming what each covers: getUserTransactions is invoice-level, getUser is profile-level, listMembershipPlans is plan definitions. An agent can route without opening any 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?

Provides an explicit 'Use when' clause (current plan, billing cycle, next due date, upgrade history, auto-renewal, past cancellations) and a 'See also' set of alternatives with the condition that separates each. It also states the required-one-of constraint between user_id and client_id and gives a default ('Default to user_id'), which is invocation-critical guidance.

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