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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered by structured data. The description adds real behavioral context beyond that: fixed newest-first ordering and, importantly, that click and domain breakdowns cost extra and only appear when named in `fields`.

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 dense sentences, front-loaded with the output shape and followed by filtering and endpoint. The metric enumeration is long but earns its place since there is no output schema; only slight trimming would improve it.

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 seven optional parameters and no output schema, the description compensates well by listing return fields and the fields-gated breakdowns. Pagination mechanics (limit/offset, next_offset) are left entirely to the schema, so it is strong but not fully self-contained.

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 71%, yet the description supplies meaning for nearly every filter: message→message_id, type→message_type, test sends→is_test, creation time→created_since. It also explains a non-obvious `fields` consequence (breakdown fields omitted unless requested), which the schema does not convey.

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: lists send reports, states ordering (newest first) and enumerates the returned metrics, so the agent knows exactly what comes back. It does not explicitly distinguish itself from the sibling vision6_get_report (single report), leaving that boundary implicit.

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 description says what can be filtered (message, type, test sends, creation time) which implies the retrieval use case, but it never states when to use this versus vision6_get_report or vision6_list_sent_contacts. No exclusions or prerequisites are given.

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