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

Annotations only supply the safety profile (readOnlyHint=false, destructiveHint=false), and the description adds materially beyond it: the return buckets (removed/not_member/not_found), the AUTO_SYNCED_LIST refusal code, the fact the operation is reversible via undo_contact_change, the $0.05 cost and API-key requirement.

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?

Six compact clauses, each carrying distinct information (identifier choice, no side effect on contacts, return shape, refusal code, undo path, cost/auth). Front-loaded with the action and resource, 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?

With an output schema, annotations, and full param coverage already present, the description covers everything an agent needs: cost, auth, failure mode, reversibility, and return buckets. Nothing material is missing for correct invocation.

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 are already documented, including the slug semantics of list_name and the 500-item cap. The description's parenthetical restates list_id/list_name but adds nothing on request_id/idempotency_key, so baseline 3 is correct.

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 ('Remove contacts from a contact list') and immediately scopes the target with list_id/list_name, clearly distinguishing it from the sibling add_people_to_list. An agent knows exactly what the call mutates and what it leaves alone ('contacts themselves are unchanged').

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?

Gives real context: which list identifier to supply, that family-style lists are refused, and the escape hatch undo_contact_change(change_id). It does not explicitly name add_people_to_list as the inverse for routing, so it falls short of full when/when-not/alternative guidance.

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