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

With no annotations, the description carries the full burden. It does disclose two useful traits — the account is passwordless and an API key is issued — but omits what happens on a duplicate email, whether the key is one-time-only or regenerable, and any rate limit or verification-email side effect.

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 padding; the action and its outcome come first. The trailing "once" is slightly ambiguous but costs little.

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 one-parameter creation tool with no annotations and no output schema, the description covers the action and the key outcome, which is enough to attempt a call. It still leaves duplicate-account behavior and confirmation/verification flow unstated.

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 0% for the single required parameter, so the description must compensate. It says nothing about the email's semantics — format, uniqueness constraints, whether it must be a real deliverable address, or whether it is used as the account identifier.

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 specific verb+resource ("Create a ... account") and adds two distinguishing traits: passwordless auth and that an API key is returned. This clearly separates it from read siblings like get_account and lookup_account, though it never names an alternative 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 guidance on when to use this versus get_account/lookup_account, nor any precondition (e.g., whether the email must be unused). Usage is only weakly implied by the verb "Create".

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