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

Annotations only supply destructiveHint=true; the description adds substantive context beyond that: it flags the mutation explicitly ('MUTATES Text-Em-All data'), states the permission requirement, and discloses that the created user is returned. It does not note side effects like invitations or rate limits, keeping it out of 5 territory.

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?

Front-loads the mutation warning and the endpoint, then handles parameters and return value in compact sentences with no filler. Slightly dense with three distinct concerns packed together, but every clause earns its place.

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?

With no output schema present, the description compensates by stating that the created user is returned, and it covers permission needs and the free-form field convention. Required-parameter behavior (0 required) is not addressed, leaving a minor gap.

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 the baseline is 3, but the description goes further by explaining the PascalCase key convention for the free-form `fields` bag and naming valid keys (EmailAddress, Permissions) that the schema itself never lists. That meaningfully reduces misuse risk for a passthrough object.

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 and resource ('adds a new user to your account') and anchors it to the exact API operation (POST /v1/account/users). It does not explicitly contrast itself with the sibling update_account_user, so it stops 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?

Gives one real prerequisite — 'a master user can do this' — which tells the agent whether the caller is eligible. It offers no routing guidance against alternatives such as update_account_user or the generic textemall_request, so usage is only partially specified.

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