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 adds useful return-field context (send time, first/last open, open type enum), but says nothing about pagination behavior or volume limits beyond the schema.

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 tight sentences, front-loaded with what is returned, then the use case and raw endpoint. The endpoint path is arguably redundant but cheap and aids traceability.

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?

A read-only paginated list tool with no output schema, so the description carries the burden of describing results and filtering. Results are sketched, but the four optional filters and pagination semantics are left entirely to the partially documented schema.

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?

With 7 parameters and only 43% schema coverage, the description should compensate, but it explains none of the filters (list_id, contact_id, report_id) or that open_type is a filter. It only indirectly references open-type values through the return-field list.

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+resource: contacts a single message was sent to, plus the fields returned (send time, open times, open type). That distinguishes it from vision6_list_contacts, though the description never names that sibling explicitly.

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?

"Use it to see who opened a campaign" gives one positive use case, but there is no when-not guidance and no pointer to alternatives such as vision6_list_contacts or vision6_get_report for aggregate stats.

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