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

Annotations already declare destructiveHint=true, indicating mutation. The description adds crucial behavioral context by stating 'This changes the user's real email subscriptions,' emphasizing real-world impact beyond the app. It also reinforces the confirmation requirement. However, it does not detail failure modes (e.g., sender lacking list-unsubscribe support) or long-term effects, though these are somewhat covered by openWorldHint. With annotations present, this description adds meaningful context without contradicting them.

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 description is two sentences long and front-loads the core action ('Unsubscribe the user...'), followed by a warning about real-world impact, then usage guidance. Every sentence earns its place with no fluff or repetition. It is concise and well-structured for quick agent parsing.

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?

The description is complete for a destructive, confirmation-gated tool. It covers what the tool does, the mechanism (one-click list-unsubscribe), the need for explicit user confirmation, and when not to use it. An output schema exists (per context) so return values do not need explanation. The only minor gap is that it does not mention potential failure conditions or whether the action is reversible, but given the output schema and existing annotations, these are not critical.

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 100%, with item_id defined as 'Inbox item id' and confirmed as 'Must be true, and only after the user explicitly approved.' The description reinforces the confirmed parameter ('confirm with them before calling') but adds no additional meaning beyond the schema. Since the schema already documents both parameters adequately, a baseline score of 3 is appropriate.

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 explicitly states the tool's action: 'Unsubscribe the user from this sender's mailing list via one-click list-unsubscribe.' It identifies the resource (the user's subscription) and the condition (this sender). It also differentiates from siblings by saying 'Use it for unwanted bulk senders, not for a person you can simply decline,' which clearly separates it from tools like inbox.decline or inbox.dismiss.

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 provides explicit usage guidance: it tells the agent to confirm with the user before calling ('confirm with them before calling') and gives a clear selection criterion ('unwanted bulk senders, not for a person you can simply decline'). This directly addresses when to use this tool versus alternatives, leaving no ambiguity about the appropriate context.

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