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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds genuinely useful behavior beyond that: all filters are exact and case-sensitive with no partial search, and results are paged with count, has_more, and next_offset. This meaningfully reduces misuse, though it could say more about default page size behavior.

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 dense sentences with the resource and returned fields front-loaded, followed by the filtering constraint, pagination contract, and endpoint. Every sentence carries information and there is no filler.

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 read-only listing tool with full schema coverage and no output schema, the description supplies the filter semantics, the pagination return shape, and the underlying endpoint. It is essentially complete; only alternative-routing detail is absent, which is immaterial to calling it 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 description coverage is 100%, so the schema already documents limit, offset, first_name, last_name, custom_fields, and opt_in_status in detail. The description reinforces the global exact-match rule, but the per-parameter semantics are largely duplicative of the schema, warranting the baseline 3.

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 (the brand's contacts/subscribers) and enumerates the returned fields, so the agent knows exactly what comes back. It does not explicitly differentiate from close siblings like slicktext_list_list_contacts, slicktext_list_segment_contacts, or slicktext_find_contact, which keeps it below a 5.

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?

There is no guidance on when to use this tool versus alternatives such as slicktext_find_contact (single lookup) or slicktext_list_segment_contacts (filtered subsets). The 'exact, case-sensitive, no partial search' note is about how filtering behaves, not about tool selection, so it does not qualify as routing guidance.

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