create_mailbox

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

Annotations already declare non-readonly, idempotent, non-destructive, but the description adds real behavioral context the annotations cannot: creation may happen via Mail or directly on the server, and the first creation in an account triggers an OS password prompt whose credential is stored in the keychain and never exposed to the agent. The auth-prerequisite disclosure is the standout value; the vague "Mail makes it when it will" leaves the exact delegation logic fuzzy.

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 verb and resource are front-loaded, which is good, but the second sentence is a long, loosely punctuated run-on that mixes fallback logic, a password prompt, and keychain behavior. It is informative rather than padded, yet the password aside could be one tighter clause.

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 two-parameter mutation with an output schema (so return values need no explanation), the description covers side effects, auth prerequisites, and path semantics. The remaining gap is duplicate-name behavior and error modes, which idempotentHint only partially implies.

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 both parameters are already documented, and the description largely restates them (the "Projects/2026" nesting example mirrors the schema wording). It does reinforce the hierarchical path semantics and the account-naming convention, but adds little beyond the schema, so 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?

The description opens with a specific verb+resource ("Make a mailbox") and immediately disambiguates what a mailbox is ("a folder, or a Gmail label"), which is genuinely useful across mail clients. It doesn't explicitly contrast with siblings like list_mailboxes or delete_mailbox, but creation versus listing/deletion is self-evident, so the gap is minor.

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?

Usage is only implied — an agent infers you call this when you need a new folder, and the path-format example gives practical invocation guidance. There is no explicit when-not guidance, no mention of what to do if the mailbox already exists, and no pointer to list_mailboxes for verifying before creating.

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