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. The description contributes one piece of added context — that the payload contains personal data (email, phone) — which is useful for handling sensitivity. It says nothing about volume, pagination behavior, or whether the list is exhaustive beyond what the schema states.

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 compact fragments with no filler; the core resource statement comes first and the endpoint path and data-sensitivity note follow. It is short without becoming a tautology, though the raw path adds little for an agent already given the name.

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 no output schema, the description carries more burden; it hints at the returned fields (email, phone) but does not describe the shape of the response or the pagination envelope that the offset/next_offset parameters imply. Adequate for a simple read, but an agent cannot fully anticipate the result.

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%: limit, offset and campaign_id are each documented, including constraints and the next_offset idiom. The description adds no parameter detail 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?

The description names a specific resource relationship: recipients attached to a campaign, backed by the endpoint GET /v1/campaigns/{campaignId}/recipients. An agent can tell it retrieves campaign recipients rather than campaign metadata or reports. It stops short of explicitly differentiating from siblings like sarbacane_get_campaign_report or sarbacane_list_contacts, but the resource is unambiguous.

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 'attached to a campaign' implies you need a campaign id and that this is a per-campaign read, but there is no explicit when-to-use guidance or comparison to alternatives such as get_campaign_report for performance data or list_contacts for the full audience. Usage is inferable but not stated.

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