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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds useful behavioral context not in annotations: the 'free' nature, newest-first ordering, and the specific classification values (interested, not_interested, out_of_office, unsubscribe, bounce). No contradiction with 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?

One dense, front-loaded sentence with no filler. It states the action, resource, cost, ordering, filters, and classification semantics in a compact form that every clause earns.

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 operation with rich annotations and a simple parameter set, the description is complete: it defines scope, ordering, filter semantics, and output classification. Pagination is implied by the limit parameter in the schema, so nothing essential 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 coverage is only 25%, so the description must compensate. It does for the two key filter parameters: campaign_id and since are explicitly described as optional filters, and since is annotated as an ISO timestamp. The remaining parameters (limit and idempotency_key) are already adequately covered by their schema metadata.

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 opens with a specific verb and resource ('Read campaign replies') and immediately adds scope: 'free', 'newest first', and optional filters. The plural 'replies' also differentiates it from the singular sibling get_reply, so an agent can distinguish them.

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?

It clearly communicates when to use this tool: to read campaign replies, with optional campaign_id and since filtersressions. However, it does not explicitly name alternatives or state when to prefer get_reply over get_replies, so it stops short of full exclusion guidance.

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