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

readOnlyHint=true already declares this a safe read, so the burden is lower. The description adds value by disclosing the shape of the result (messageID, sentOn, sentTo group, recipientCount) and the messageID linkage to other reports, but says nothing about pagination behavior despite the pp/page parameters.

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?

Four terse, front-loaded fragments with essentially no filler; the returned-field list and the messageID tip come first. It is telegraphic rather than wasteful, though the fragmentary style slightly hurts readability.

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 compensates by enumerating the returned fields and the key messageID, and annotations cover the safety profile. Only pagination and the 'last' start-date behavior are left unaddressed, which is a minor gap for an all-optional, fully-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?

Schema description coverage is 100%, so all five parameters are already documented in the schema (pp, to, from with 'last', page, subaccount). The description only restates the YYYY-MM-DD date format and adds nothing about the 'last' keyword or subaccount semantics, so 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?

States a specific verb+resource (list sent messages/campaigns) and enumerates the returned fields, so it is distinguishable from list_received_messages and list_scheduled_messages. It does not explicitly name the sibling it contrasts with, but the scope 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 line 'The messageID is what the delivery and click reports need' implies a downstream workflow with get_delivery_report/get_click_report, which is useful routing context. However, it never says when to choose this over get_sent_summary or the received/scheduled list siblings, so usage is only implied.

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