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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds little beyond restating that these are received mailings and citing the GET path, which duplicates what readOnlyHint already tells the agent; pagination behavior is only implied through the 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?

A single front-loaded clause states the resource before any qualifier. The trailing 'GET /members/{key}/mailings' is mildly redundant with readOnlyHint but does anchor the endpoint.

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 should say more about what a mailing record contains (subject, date sent, date opened) — it gestures at 'what was sent and when' but not the shape. For a paginated, four-parameter read tool this is adequate but leaves the return payload underspecified.

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% — key, page, sort enum, and limit are all documented in the schema, including the 'pass the previous reply's next_page' hint. The description adds no parameter meaning beyond that, so the 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?

States a specific verb-like resource and scope: mailings received by a specific member, with the parenthetical clarifying it shows what a contact was sent and when. It is distinguishable from cyberimpact_list_mailings (account-wide) and cyberimpact_get_mailing (single mailing), though it never names those siblings explicitly.

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 '(use it to see what a contact was sent and when)' gives an implied use case, but there is no explicit when-not guidance and no named alternative (e.g., list_mailing_recipients for the inverse direction). The agent must infer routing from the resource name alone.

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