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

Annotations already establish readOnly, non-destructive, closed-world behavior, so the bar is low; the description nevertheless adds real domain semantics beyond them — that past_due means a failed payment is being retried, that canceled members retain access until the paid period ends, and that MRR normalizes yearly plans by a twelfth. Pagination and result limits are not covered, but the status and aggregation semantics are substantive added value.

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?

It is a single front-loaded sentence with no filler, and the field list is ordered from identity to status to billing. The nested parentheticals make it dense and slightly harder to scan, but every clause carries information.

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 correctly carries the return-value burden and describes the returned fields and aggregates in detail. What it omits — pagination, result caps, and any note about the required product argument — is minor given annotations already cover the safety profile.

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% for both parameters, so the schema already documents the product id/slug/title and workspaceId default. The description only echoes 'membership product' without adding format or resolution guidance, so the baseline of 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 names a specific resource — subscribers of a membership product — and enumerates the exact fields returned, which makes the read/list intent unambiguous even though the sentence itself contains no verb. It is distinguishable from neighboring list tools (list_contacts, get_audience, list_team) by scoping to a membership product's subscribers, though it never explicitly contrasts itself with them.

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 tool versus alternatives, no prerequisites, and no mention of the product identifier requirement. The agent must infer usage entirely from the title and name.

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