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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds the meaningful 'requires read scope' auth requirement, but says nothing about pagination behavior or result ordering beyond what the schema implies.

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 short sentences, front-loaded with the core action, with no redundant wording. It is perhaps too terse given the crowded sibling namespace, but nothing is wasted.

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 simple parameterless-required read tool with full schema coverage and read-only annotations, the key omission is disambiguation from search_contacts and the campaign-scoped variants. The auth-scope note helps, but an agent could still reasonably call the wrong contact-listing tool.

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%, with page, page_size, and search all documented including defaults and max bounds. The description only echoes the search parameter, adding no meaning beyond the schema, so the baseline of 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 clear verb and resource: listing contacts, with the search capability noted. It does not distinguish itself from the similarly named siblings search_contacts or list_campaign_contacts, so the agent cannot tell from the description alone which one to pick.

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?

'optional search' implies the tool can also filter, but there is no guidance on when to use this versus search_contacts or the campaign-scoped listers. No prerequisites or exclusions are stated beyond the scope note.

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