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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered; the description adds real context beyond that with the page size (50) and the exact result payload. It omits how pagination ends or what next_page/total look like, a minor gap.

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 tight sentences with the resource and page size front-loaded and no filler. The trailing 'Sort and filter by the extra fields' is imprecise phrasing that costs it a bit of clarity.

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 usefully enumerates the returned fields and the page size, which is what an agent needs to call and consume it. It does not mention pagination termination or the endpoint's response envelope, a small residual gap.

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 each parameter is documented there, including the enum sort orders and the next_page hint, so baseline is 3. The description's 'sort and filter by the extra fields' is vague and slightly at odds with the enum (which sorts by email/name/position/points), adding little beyond the schema.

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?

Names a specific verb (List) and resource (subscribers of a campaign) and enumerates the fields returned, so the agent knows exactly what it yields. It does not explicitly differentiate from siblings like get_subscriber or search_subscribers_by_name, though 'of a campaign' implies a bulk listing.

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?

It states the pagination cadence (50 per page) and that sorting/filtering is available, which implies when to use it for browsing a campaign's subscriber base. However, it never says when to prefer this over search_subscribers_by_name or get_subscriber_by_email, leaving the routing to inference.

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