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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the safety profile is carried by structured data. The description adds the domain constraint (@cherami.to) and the human-collaboration note, but says nothing about the non-idempotent behavior or what creating an inbox affects. With annotations covering the baseline, a 3 is appropriate.

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?

A single front-loaded sentence with no filler; the verb and resource lead immediately. It is efficient, though the trailing "with the human" phrasing is slightly oblique for the amount of information it carries.

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?

An output schema exists, so return values need not be described, and the schema covers parameters thoroughly. However, for a creation tool with no annotations on side effects beyond hints, the description omits any mention of the human-confirmation flow's implications or collision/duplicate behavior, leaving it minimally adequate.

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%, so all four parameters (including name vs sender_name distinctions and idempotency_key replay semantics) are already documented in the schema. The description only gestures at "the address" without adding format, immutability, or casing details beyond what the schema states, so the baseline 3 applies.

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 ("Create an @cherami.to inbox") and scopes it to a domain-qualified address, so it reads distinctly from the many message/draft tools in the sibling list. The clause "at the address chosen with the human" is unusual but does narrow the intent. It stops short of explicitly differentiating itself from update_inbox or list_inboxes.

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?

There is no statement of when to use this versus update_inbox or list_inboxes, and no prerequisites or error/duplicate conditions. The only contextual hint is the implied human-in-the-loop address selection. An agent is left to infer the appropriate call site.

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