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

Annotations already declare readOnlyHint=true, so safety is covered; the description adds the pagination model (cursor page) and the underlying REST endpoint, which is real context beyond annotations. It does not state default page size, max limits, or rate-limit behavior, so it is not fully transparent.

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 with the purpose and pagination behavior front-loaded and no filler. The endpoint reference is compact and skippable for agents that don't need it.

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 3-parameter read-only list tool with full schema coverage, the description covers purpose, scoping, and the paging model. With no output schema, it leaves the actual response shape (e.g., what next_cursor is returned alongside) only implied rather than stated.

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 limit, audience_id, and starting_after are already documented, including the reference to next_cursor. The description's 'cursor page' phrasing reinforces starting_after but adds no syntax or edge-case detail, 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 (List), resource (contacts), and scope (belonging to a static audience) rendered as a cursor page. The 'static audience' qualifier cleanly separates it from bird_list_contacts, so an agent can route without opening either schema.

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 'static audience' scoping implicitly tells the agent this tool is for audience-scoped listing and not for the dynamic/segment case, and it names the parent resource. There is no explicit 'use X instead when Y' routing to a sibling, so it stops short of a 5.

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