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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds genuinely useful context beyond that: it discloses pagination shape ('returns exact total and bounded pages') and a data-exposure constraint ('does not expose email or provider identifiers').

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, tightly front-loaded with the core purpose before the return/data caveats. Every sentence carries distinct information with no redundancy.

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 compensates by describing the return shape (exact total, bounded pages) and privacy limits, which is what an agent needs to consume results. A minor gap is that it doesn't clarify behavior when list_id refers to an archived or missing list.

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 limit, offset, and list_id are already fully documented in the schema. The description's mention of 'bounded pages' loosely relates to the paging parameters but adds no syntax, format, or defaults beyond what the schema provides. 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) and resource (contacts) with clear scoping to 'one unarchived list in the selected product', which distinguishes it from list_lists and get_list. It does not explicitly name the sibling it differs from, but the resource specificity makes the intent unambiguous.

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 resource statement — you call it to enumerate contacts in a given list — but there is no explicit when-to-use guidance or exclusion against alternatives like get_list, find_leads, or search_external_leads. Adequate but leaves selection to inference.

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