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

Annotations already indicate this is a mutating, non-idempotent, open-world operation. The description adds that Cooper POSTs on mail received or sent, which is useful behavioral context, but it does not disclose effects like overwriting existing webhooks, authentication needs, or response format. It adds modest value beyond annotations.

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 primary action and scope. No filler or redundancy; every word earns its place.

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 and sparse annotations, the description must carry more weight. It omits critical details about the events parameter, possible validation rules, and whether repeated calls replace or duplicate webhooks. An agent cannot fully understand how to invoke it correctly without extra inference.

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 0%, so the description must explain parameters. It mentions 'HTTPS URL' for the url parameter, but does not explain the events parameter at all, nor its enum values. The description fails to clarify that events can be filtered to specific message/task events, leaving agents to guess.

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 clearly states the tool registers an HTTPS URL for webhook delivery on mail events, with a specific verb ('Register') and resource ('webhook'). It is distinct from sibling tools like send_message or list_inboxes, and the purpose 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 description implies usage for setting up webhook notifications but provides no explicit guidance on when to use this tool versus alternatives, nor any exclusions or prerequisites. The sibling set is diverse, but no routing guidance is given.

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