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

Annotations already declare this is a non-read-only, open-world, non-idempotent, non-destructive operation. The description adds useful behavioral context beyond that: the owner receives an 8-digit email code, and confirm returns or consumes the key once. It does not describe permissions, duplicate-account behavior, or rate limits, but it meaningfully clarifies the mutation workflow.

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 short and front-loads the main outcome, then breaks down the two actions. It has some redundancy between the first sentence and the action bullets, and the phrase “answers the key once” is slightly awkward, but there is no significant bloat.

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 an 11-parameter mutation tool with no output schema, the description covers the essential action flow, prerequisites, and email-code behavior. The detailed signup fields are left to the fully described schema, and the remaining gap is mainly that the return value beyond the one-time key is not explained.

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 the input schema already documents the parameters in detail. The description adds some action-level grouping by noting that email and code are needed for confirm and kind is needed for signup, but it largely refers the agent back to the action and its arguments rather than expanding parameter meaning.

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 and resource: opening an account for the owner. It also distinguishes the two supported actions, signup and confirm, with their basic outcomes. It does not differentiate this tool from the similarly named sibling commercebook_start, so it falls short of a 5.

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 clearly explains when to use each action: signup requires no key and takes a kind, while confirm requires the email and 8-digit code. It gives enough context to choose between the tool’s two actions, but it does not mention when not to use the tool or when an alternative sibling tool is more appropriate.

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