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

The destructiveHint annotation already flags this as a mutating call, and the description reinforces and extends it with 'MUTATES Text-Em-All data', the specific HTTP verb/route, the note that user_id is never sent in the body, and the return value ('Returns the updated user'). It stops short of describing reversibility or field-level side effects, so not 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?

Front-loads the most important fact ('MUTATES Text-Em-All data') and packs the route, field-passing convention, and return value into three tight sentences with no filler. Slightly dense with parenthetical asides but every element is load-bearing.

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 mutating tool with no output schema, the description covers the essential call mechanics: identity parameter placement, how to express changes, and the shape of the response. It leaves out failure modes and permission requirements, but the destructiveHint annotation and full schema coverage carry much of that burden.

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 four parameters are already documented, making 3 the baseline. The description adds only marginal value: PascalCase naming convention and examples (EmailAddress, Permissions) not present in the schema, and confirms that fields are merged over typed fields. It does not explain the precedence or behavior of the open-ended `fields` bag beyond what the schema says.

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 ('updates an existing account user') plus the underlying API route (PUT /v1/account/users/{user_id}), so an agent immediately knows what the tool does. It does not explicitly distinguish itself from the sibling add_account_user, which is the create-side counterpart, 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?

Usage is implied by 'updates an existing account user' and the PUT verb, and the description tells the caller how to pass changes via `fields`. However it never states when to use this tool rather than add_account_user, nor any prerequisites (e.g. the user must already exist) or exclusions.

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