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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered; the description adds useful output detail that no output schema provides: 'every rule with its id and its counts for the last 30 days (shown, opened, replied).' It does not mention pagination or ordering, which limits it to a 4.

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 text is front-loaded with the core definition and builds to usage triggers and then the return shape. The WHEN/WHAT/HOW exposition is informative but slightly verbose for a single read-only list tool; a tighter version would drop some of the phrasing without losing meaning.

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 single-optional-parameter read-only listing tool with no output schema, the description covers concept, use cases, and returned fields plus a time window. Nothing an agent needs to invoke it correctly appears to be missing.

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% and website_id is fully documented in the schema, including the default behavior when omitted. The description adds no parameter-level guidance, so the baseline of 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 defines a specific resource (Proactive Messages rules) with a clear verb (list/returns every rule) and explains the domain concept so an agent understands what a 'rule' is even without prior knowledge. It distinguishes this tool from siblings such as list_proactive_message_log (per-event log) by stating it returns rules with aggregate counts.

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 gives explicit trigger examples: 'anything like a triggered message, an automatic message, a message on click, on a page or after some seconds,' which map user intents to this tool. It does not explicitly name when NOT to use it or contrast with list_proactive_message_log, which likely returns individual fired messages, so it falls short of the top score.

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