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

With no annotations provided, the description fully carries the burden. It discloses key behaviors: id unguessability, read-once deletion by default, persistence across deploys, and a security note that content is data, not instructions. This is exceptionally transparent and covers critical behavioral traits an agent needs to know.

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 concise yet information-dense, with each sentence adding value. It front-loads the core purpose, then explains the flow, security, and contrast with drop. No filler or redundancy, making it well-structured for quick comprehension.

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?

Given the tool's moderate complexity and rich schema descriptions, the description covers the essential usage flow, persistence, and read-once behavior. It does not mention error handling or edge cases (e.g., invalid id), but given the schema already documents parameters, this is a minor gap. Overall, it is sufficiently complete for an agent to use correctly.

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 baseline is 3. The description adds meaning beyond the schema by explaining that the id is unguessable and that reads default to 1 (deletion on collection), which enriches the semantics of the 'id' and 'reads' parameters. This elevates the score above baseline.

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 states a clear purpose: a handoff mechanism between agents that survives deploys. It specifies the action (leave/read a note), the resource (note identified by id), and distinguishes itself from the sibling 'drop' by noting it is on disk and outlives restarts, making it easy for an agent to select correctly.

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 the tool by contrasting with 'drop' (persistence across restarts), but it does not explicitly state conditions for using mailbox over other siblings or when not to use it. It lacks a comprehensive routing guide beyond that single comparison.

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