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

Annotations already declare the safe read-only, idempotent profile, and the description adds substantial non-derivable behavior: a page holds at most limit contacts AND at most 25,000 characters, so it may return fewer than requested; pagination.next_cursor/has_more drive continuation; and oversized contacts appear in pagination.omitted.

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?

Front-loads verb and scope, then layers pagination and edge-case behavior in one dense but well-ordered sentence. The parenthetical field enumeration earns its place given there is no output schema, though the sentence is long.

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 available, the description covers the return shape (enumerated fields), page-size limits, continuation mechanics, and the omitted-contact edge case, giving the agent everything needed to call and consume the tool 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 coverage is only 50%, but the description compensates by explaining what limit actually bounds (contacts and characters per page) and how cursor relates to pagination.next_cursor. contact_list_id semantics remain only implied, and organization_id relies on 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 and resource ('List one bounded page of a contact list's contacts') and clarifies scope with fields, ordering ('import order'), and record source ('using the REST contact record'). It is clearly distinguishable from list_contact_lists and get_contact_list without opening any 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?

Usage is implied by the scoping to a single contact_list_id, and the pagination narrative tells the agent how to continue, but no alternative tool is named and there is no explicit when/when-not guidance. Adequate but not routing-grade.

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