defender_get_user_machines

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

Annotations already declare this a safe read-only operation, and the description adds useful semantic context by clarifying that the results are historical logon relationships rather than roles or privileges. This prevents an agent from misinterpreting the output as current access assignments, which is valuable beyond the readOnlyHint.

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?

A single sentence that leads with the action and resource and packs the essential semantic distinction into a tight colon clause. There is no filler or redundant restatement of the tool name.

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?

Given the simple read-only list purpose, fully documented parameters, and safety annotations, the description is mostly sufficient. It lacks an explicit statement of the return shape or pagination behavior, but the tool name and schema make the call correct without that detail.

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?

All three parameters are fully described in the schema, including the meaning of user_id as the account name as Defender reports it. The description itself adds no parameter-level detail, so it meets the baseline for high schema coverage without augmenting it.

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 – 'List the devices a user logged on to' – and adds a clarifying contrast, 'logon relationships, not role or privilege.' It is clear but does not name or differentiate from the closely related sibling defender_get_machine_logon_users, so it stops short of the strongest sibling-aware framing.

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 provides no guidance on when to choose this tool over the many sibling get_* tools, nor does it mention the inverse tool defender_get_machine_logon_users or any alternative for assigned devices. The only implied context is that the tool is for logon history, not entitlements.

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