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

With no annotations, the description carries the behavioral disclosure burden. It clearly discloses partial-update semantics ('Omitted fields are left unchanged'), the admin owner_key requirement, and that role_ids is a whole-combination replacement. It does not describe the response or explicit-null behavior, but the core mutation behavior is transparent.

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?

Three tight sentences with no filler. The action and target fields are front-loaded, and the key behavioral notes are stated directly afterward.

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?

The description is sufficient for a focused update tool: it names all updatable fields, states partial-update behavior, and notes the auth requirement. Minor gaps are the unexplained 'bundle-26' reference and the lack of response/return information, but the schema covers all parameters.

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 schema already documents each parameter's meaning. The description adds useful grouping and reinforces the replace-versus-omit behavior, but it does not introduce significant new parameter-level detail beyond the schema.

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 names a specific verb ('Reassign') and resource ('access_key'), and lists the exact updatable attributes: role_ids, mailbox_label, and expiry. This clearly distinguishes it from sibling tools like create_access_key, revoke_access_key, and list_access_keys.

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 makes the usage context clear: this tool updates an existing access key's attributes, with omitted fields left unchanged. It states an important prerequisite (admin owner_key required) but does not explicitly say when to prefer create_access_key or revoke_access_key over this tool.

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