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

Annotations already declare readOnlyHint=true, so the safety profile is covered and the bar is lower. The description adds the upstream endpoint (GET /contacts) and notes the list is scoped to the 'shared address book', but says nothing about pagination behavior, result caps, or empty-result handling beyond what the schema shows.

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 with no waste, and the core purpose is front-loaded before the endpoint reference. The REST endpoint note is marginally useful but slightly non-essential.

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 list tool with 100% schema coverage and no output schema, the description supplies enough to call it correctly. Only the lack of any note on pagination/result limits keeps it from being fully complete.

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 all five parameters (from, to, page, order, per_page) are already fully documented in the schema. The description only gestures at the date window and ordering, adding no format or default detail beyond the structured fields. Baseline 3 is appropriate.

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 contacts in the shared address book') plus the optional filtering dimension, so the agent knows this is a bulk read. It implicitly contrasts with aircall_get_contact (single) but never names siblings such as aircall_search_contacts, so the differentiation is left to inference.

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 phrase 'optionally by creation-date window and order' hints at the appropriate use case, but there is no explicit when-to-use versus aircall_search_contacts or aircall_get_contact, and no exclusions or prerequisites. Usage is implied rather than stated.

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