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

Annotations already declare readOnlyHint=true, and the description reinforces this with the GET endpoint and resource path. The word 'currently' usefully signals that membership is evaluated live against segment criteria rather than a static list, but nothing is said about result size, pagination, or what happens for an empty/invalid segment.

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: purpose first, then the concrete API mapping. Nothing is redundant and nothing is buried.

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 two-parameter read tool with no output schema, the description covers what it does, its scope, and the underlying endpoint. It is slightly thin on result behavior (pagination/limits), but an agent has enough to invoke it correctly.

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%, so both parameters (segment_id, mailing_list_id) are fully documented in the schema, including their provenance tools. The description only restates the identifiers via the URL template and adds no format or constraint detail 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?

States a specific verb (List) and resource (subscribers), with the scoping condition 'that currently match one segment's criteria' distinguishing it from moosend_list_subscribers. It does not name the sibling tool explicitly, so it is clear but not fully differentiated.

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?

Usage is implied by the phrase 'match one segment's criteria' – an agent infers this is for segment-scoped lookups – but there is no explicit when-to-use, when-not-to-use, or named alternative (e.g. use moosend_list_subscribers for the whole list).

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