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

Annotations already cover safety profile (readOnly=false, idempotent=true, destructive=false, openWorld=true), but the description adds real behavioral context beyond them: it never takes a lease, never steals a live message, and that empty string clears a field. The clear-value semantics and lease-safety guarantee are not derivable from the 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 dense sentences, front-loaded with the primary action and the key differentiator. The parenthetical slash-list of webhook fields is compact but slightly cramped; nothing is wasted.

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 9-parameter tool with a nested object and no output schema, the description conveys the core behavior and the anti-lease guarantee but leaves six parameters semantically undocumented and never states defaults or what happens when no fields are supplied. Adequate but with clear gaps.

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 only 33% (3 of 9 params documented), so the description must compensate, and it partially does by naming accept_from, harness, and the webhook_* trio plus the '"" to clear' convention. It omits meaning for 'as', 'machine', 'session_ref', and 'accept_wake_from' (including the ["*"] default), so half the surface remains unexplained.

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 and resource ('change your OWN mailbox settings'), names the concrete fields it touches, and explicitly distinguishes itself from the sibling bus_inbox by the no-lease constraint. An agent can pick this over bus_inbox without opening either schema.

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 contrast with bus_inbox ('Same fields as bus_inbox's settings, but this tool can never take a lease, so configuring never steals a live message') gives a clear condition for choosing this tool over the alternative. It lacks an explicit 'use this when / not when' phrasing but the routing logic is unambiguous.

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