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

With no annotations, the description carries the full burden; it discloses sort order ('most recently blocked first') and that each entry includes the day blocked, which is real behavioral value. It never states that this is a read-only operation, whether results are paginated or capped, or what permissions are needed to see account-level blocks.

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 sentences, front-loaded with the concrete result and ordering, then a short justification for why the list matters. The second sentence leans slightly rhetorical ('a rule the account is living under becomes visible again') but still conveys the deleted-thread edge case.

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?

Zero parameters and no output schema, so the description must explain the return set itself — it does: addresses, sort order, and the blocked date. Only paging/limits and the read-only nature are left unstated, which are minor for a simple list 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?

The tool takes no parameters, so there is nothing for the description to clarify and the baseline of 4 applies. Nothing in the text misdescribes the (empty) input surface.

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?

Names a specific verb and resource ('Lists the addresses whose mail this account files straight into Spam') and ties the concept to report_spam's output, so an agent knows exactly what it gets. It stops short of distinguishing the list from close siblings such as list_suppressed_recipients or list_sender_addresses, which are the realistic confusion points.

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 framing ('this is where a rule the account is living under becomes visible again') implies when the tool is useful, especially for blocks surviving deleted threads. But there is no explicit when-to-use/when-not against siblings like list_suppressed_recipients or unblock_sender, so the agent must infer the routing.

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