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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered; the description adds genuinely new behavioral context: newest-first ordering, the per-entry fields, that name/email only appears when the site sends User Context, and that replied entries carry a conversation link.

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?

The resource and ordering constraint are front-loaded, and the long enumeration of returned fields is dense but informative. The closing sentence earns its place by stating purpose; no filler sentences.

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 the burden of describing return values, and it does so thoroughly: fields, ordering, conditional visitor identity, and linked conversations. Pagination and limits are left entirely to the schema, which is a minor gap for a log-listing tool.

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 100%, with limit bounds, rule_id filtering, before_id cursor semantics and website_id defaulting all documented in the schema. The description adds no additional parameter meaning beyond mentioning 'the rule' as a returned field, 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?

The description states a specific resource and what each record represents: 'each proactive message a visitor saw', framed as an exposure log rather than a rule configuration. This implicitly separates it from list_proactive_messages (the rules), but it never names that sibling, so an agent must infer the distinction.

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 saw a message and whether a rule works' gives a concrete use case that fits the tool well. It does not state when-not to use it or point to list_proactive_messages for editing/reading the rules themselves, leaving that routing to inference.

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