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

readOnlyHint=true in annotations already establishes this as a safe read. The description adds value by clarifying that the response covers segment criteria rather than member records, but says nothing about auth requirements, error behavior, or response shape for a tool with no output schema.

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 compact sentences: the first carries purpose and scope, the second carries endpoint identity. Nothing is redundant and the disambiguating clause is front-loaded.

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-required-param read tool with no output schema, the description covers what is fetched and what is not, which is enough for correct invocation. Only auth/permission expectations and response format are left implicit.

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 already documents its type and source tool (segment_id from list_segments, mailing_list_id from list_mailing_lists). The description adds no parameter-level detail beyond the schema, so baseline 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?

Specific verb + resource ('Get one segment's details and criteria') with an explicit scope exclusion ('not its members') that separates it from the sibling moosend_list_segment_subscribers. The Moosend REST path reinforces exactly which resource is fetched.

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?

The parenthetical 'not its members' implicitly routes the agent to list_segment_subscribers when members are wanted, and it contrasts with list_segments by fetching one entity. No explicit 'use this when / do not use when' phrasing or prerequisites are stated.

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