create_mailbox

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

With no annotations, the description carries full burden. It discloses that the tool is not idempotent, returns 'mailbox_settings' and 'next_actions' under certain conditions, and surfaces specific errors. This adds meaningful context beyond the input schema, though it could mention required permissions or rate limits.

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, front-loaded with the main purpose, and includes essential behavioral notes. Every sentence earns its place with zero redundancy or fluff.

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 simple creation tool with two parameters and no output schema, the description adequately covers purpose, non-idempotency, return values, and error conditions. It could be more complete by specifying the authorization context, but the current level is sufficient for an agent to execute 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?

The input schema already provides detailed descriptions for both parameters (project_id and slug) with format constraints, achieving 100% coverage. The tool description repeats the slug format but adds no new semantic info beyond what the schema offers, so baseline 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 clearly states the verb 'Create' and the resource 'project-scoped email mailbox' with a specific format (<slug>@mail.run402.com). It distinguishes this creation action from sibling tools like 'delete_mailbox', 'get_mailbox', and 'list_mailboxes' by emphasizing non-idempotency and error surface.

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 some usage context by noting non-idempotency and potential errors (slug conflicts, cooldowns, limits), but it does not explicitly guide when to choose this tool over alternatives (e.g., use for creation, not for modification or deletion). Sibling tool names are available but not referenced.

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