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

Annotations already declare idempotentHint=true and destructiveHint=false, so the safety profile is partly covered. The description adds useful behavioral context beyond them: partial updates leave fields unchanged (matching the null parameters) and the reply's `active` field reports what actually got activated, which is genuine non-obvious behavior.

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 sentences, front-loaded with the core action, then provenance, then the non-obvious activation caveat. Dense and mostly waste-free, though the final sentence is slightly long for what it conveys.

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 an output schema present, return-value docs aren't needed, and the description still hints at the reply's `active` field. Combined with full schema coverage and annotations, an agent has what it needs; only the absence of explicit alternative routing keeps it from a 5.

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%, and each parameter already documents 'null = leave unchanged' and 'Never guess one'. The description only adds the provenance of the numbers (list_beans/list_grinders/list_machines), which largely duplicates the schema, so the baseline 3 applies.

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 ('switch the active') and resource (bean, grinder, machine) for this account, and explicitly sets it apart from the register_* siblings by noting that registration only activates when nothing of that kind is in use. An agent can tell this is the explicit activation setter, not a create/update tool.

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 clear context for when to call it: to start using something new (after registering) as well as to switch back to an existing item. It also points to the list_* tools that supply valid numbers, but doesn't enumerate alternatives such as update_bean or set_grinder_position for other forms of change.

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