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

The description asserts the operation is "reversible" while the annotation declares destructiveHint=true, which undercuts the safety signal an agent should surface before mutating a user. The "sends no notification" clause is genuinely useful added context, and it does not state whether the PUT is a full replace or a partial merge, nor any permission/rate-limit constraints.

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?

Two short clauses with the core verb front-loaded and no filler; the API-endpoint parenthetical is compact and helps map the call. Slightly more terse than ideal, but nothing is wasted.

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 8-parameter mutation with no output schema, the description covers the basic nature of the call but omits replace-vs-merge semantics, required permissions, and error/partial-update behavior, and its reversibility claim conflicts with the destructive annotation. Adequate but with clear gaps.

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 all eight fields (including custom_attributes and detailed phone_numbers/timezone formats) are already documented in the schema; the description adds only the implied path placement of user_id via PUT /users/{user_id}. Baseline 3 applies when the schema does the heavy lifting.

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?

"Updates a user record" is a specific verb+resource that clearly separates it from magicbell_create_user, magicbell_get_user, and magicbell_list_users, and the projected PUT /users/{user_id} endpoint reinforces the operation type. It does not explicitly name a sibling, but the change-vs-create-vs-read distinction is unambiguous from the text.

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 purpose implies when to reach for this tool (mutating an existing user), but there is no explicit when-to-use/when-not guidance or pointer to alternatives such as magicbell_create_user for new records or magicbell_get_user for reads. Usage is inferable rather than stated.

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