Create Mail User

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

Annotations already declare write (readOnlyHint=false), non-idempotent, non-destructive, open-world behavior. The description adds a genuinely non-obvious side effect beyond that: 'Flushes MCP cache.' It does not cover auth/permission requirements or behavior when the key already exists, so it stops short of a 5.

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?

Three labeled lines (Purpose / Inputs / Side effects), each front-loaded and information-dense. No filler, no repetition of schema or annotation data.

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 3-param mutation with annotations and no output schema, the definition covers endpoint, required inputs, settings fields and a side effect. Gaps remain around permission requirements and failure modes (duplicate key), but nothing critical to correct invocation is missing.

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% for the two required params, and the description usefully enumerates fields inside the opaque `settings` object (password, status, type, displayname) — information the schema's 'User fields' with additionalProperties:{} does not provide. It points to the engine OpenAPI rather than fully specifying settings, so not a 5.

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+resource ('Create mailbox user') and pins it to the exact REST endpoint POST /v1/domains/{domain}/users/{key}). The 'create' action plus the users.* sibling family makes it easy to separate from users.get/update/delete/list, though it never names those siblings explicitly.

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 when-to-use or when-not-to-use guidance, no mention of prerequisites (e.g. domain must already exist), and no routing to alternatives such as users.update when the mailbox already exists. The structured 'Inputs' block is parameter documentation, not usage guidance.

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