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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds genuine context beyond that: the sent-state default excludes archived mailings, the returned fields (id, subject, language, send/schedule date, recipient count, sender), and the underlying GET endpoint shape.

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?

Three short sentences, no filler: scope enumeration first, returned fields second, optional filter last, with the endpoint as a trailing technical cue. Every sentence carries information an agent needs.

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 schema fully covers pagination/sort parameters. For a read-only list tool this is close to complete, though it doesn't say anything about page-size defaults or result ordering behavior beyond pointing at the sort enum.

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%, so baseline is 3, but the description expands the terse 'Which mailings (default sent)' enum note into per-state meanings, and adds the non-obvious fact that sent implicitly filters out archived. Page/sort/limit are left entirely to the schema, so the gain is real but partial.

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?

The description opens with a specific verb+resource ('List mailings') and immediately enumerates the three scopes it can return, including the default. An agent can tell this is the listing tool rather than a single-mailing fetch, though it never names a sibling (e.g. get_mailing) to sharpen the boundary.

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 clarifies what each state means — sent excludes archived, scheduled is 'queued to go out' — and notes the group filter is optional, which implies how to pick a scope. But it gives no explicit when-to-use vs alternatives (get_mailing, list_mailing_recipients) and no exclusions beyond the sent/archived default.

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