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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered without help from the prose. The description adds pagination behavior via 'Paged: use next_start', which is genuine added context, but says nothing about ordering, empty results, or what a member record contains. Adequate against a lower annotation-adjusted bar, not rich.

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 short sentences, zero filler, with the disambiguating scope parenthetical placed immediately after the resource so the reader hits it first. The pagination note trails as a secondary operational detail, which is the right ordering.

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 simple read-only list with fully documented parameters and no output schema, the description covers purpose, scope, and pagination — enough to call it correctly. It leaves the shape of returned member records and result ordering unstated, a minor gap given how shallow the operation is.

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% and all three parameters carry their own descriptions with ranges and defaults, so the schema does the heavy lifting. The description's 'Paged: use next_start' merely echoes the schema's own start-parameter text ('Use next_start from the previous reply'), adding no new semantics. Baseline 3.

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 (list) and a precisely scoped resource (the individual members a mailing was sent to), and pre-empts confusion by excluding groups and searches. That negates the ambiguity with siblings like emma_list_members, emma_list_group_members, and emma_get_search_members in the same sentence.

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?

'(not groups or searches)' gives a clear scope boundary that implicitly routes the agent to the group/search-member siblings, and 'Paged: use next_start' tells the agent how to iterate. It stops short of naming an explicit alternative tool or stating when-not to call this one at all, so it is strong but not a full routing statement.

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