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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered structurally. The description adds the returned payload shape, but says nothing about pagination behavior, result caps, or auth/scope requirements — modest added value beyond the annotations.

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, front-loaded fragments with zero filler: purpose, return fields, filters, and endpoint. Nothing redundant and nothing buried.

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 zero-required-parameter list tool with full schema coverage and a safety-carrying annotation set, the description covers purpose, filters and returned fields adequately. Since there is no output schema, marginally more detail on the response envelope (e.g. next_offset) would fully close the gap.

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 limit/offset/order_by/campaign_id/message_type are all documented in the schema itself. The description only gestures at type and campaign filtering and adds no format or interaction detail beyond that, so the 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?

Specific verb+resource ('List messages') with the returned fields enumerated (subject, type, campaign, create date, bodies) and the underlying endpoint (GET /messages). It does not explicitly distinguish itself from the sibling icontact_get_message, but the list/get contrast is strongly implied.

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?

'Filter by type or campaign' tells the agent the two narrowing dimensions, which is useful usage context. It never says when to prefer this over icontact_get_message or icontact_list_message_activity, so routing is left to inference.

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