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

Annotations already indicate write/destructive behavior, but the description adds critical context: it writes to a shared workspace visible to all callers, and the effect is persistent ('standing rule'). This goes beyond the annotations by explaining side effects and cross-caller visibility. It also states the return value, consistent with the output schema. No contradiction.

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 three sentences with no wasted words. It front-loads the core action, then explains the persistent nature and shared-workspace side effect, and finally points to the deletion tool. Each sentence earns its place, making it efficient and well-structured.

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 covers the tool's purpose, its long-term effect, the shared workspace implications, and how to reverse it. Given the presence of an output schema and 100% parameter coverage, nothing critical is missing. An agent can confidently decide when to use this tool and what consequences to expect.

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%, so all parameters are already documented. The description adds minimal parameter-level detail beyond restating that it adds an 'address or domain' (matching `entry`) and 'allow or block' (matching `type`). It does not clarify `direction` or `reason` beyond schema descriptions. With full schema coverage, a baseline of 3 is appropriate; the description does not substantially enhance parameter understanding.

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 action: 'Adds one address or domain to an inbox's allow or block list and returns the created entry.' It identifies the resource (inbox list) and the specific operation (create entry). It also mentions the sibling delete tool, helping distinguish from removal. The purpose is unambiguous and specific.

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 context on when to use it: it creates a standing rule affecting mail acceptance/sending. It explicitly says to remove one with `delete_agentmail_inbox_list_entry`, guiding towards the delete alternative. However, it does not mention the sibling `post_agentmail_list_entry` (likely a global list variant), so it does not fully differentiate between similar create tools. Still, the usage context is clear.

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