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

Annotations already establish mutation, idempotence, and non-destructiveness; the description adds useful domain context: registering something automatically makes it active, so set_active is for switching to existing entries. It does not contradict annotations. This extra context goes beyond what the annotations alone convey.

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 short sentences, front-loaded with the verb and object, followed by the source rule and a usage caveat. No filler or repetition of annotation fields.

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 plus rich schema and annotations covers selection and safe invocation for bean/grinder/machine, and the output schema removes return-value ambiguity. The only notable gap is that program_id is missing from the description, so an agent focused on programs might not recognize set_active as the right tool.

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 baseline is 3; each param already carries an exact source and null semantics. The description's 'numbers come from list_*' note reinforces the schema but mainly duplicates it, and it omits the program_id source (active machine's list).

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 clear action ('Switch the active bean, grinder or machine') with account scope, and the source-of-truth sentence distinguishes it from list_* and register_* siblings. However, it omits program_id, which the schema lists as a settable field, so the stated resource set is incomplete.

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?

Explicitly tells the agent when to use it ('switch back to something that exists') and when not to ('not after register_coffee'), naming the list_* tools as the source for valid IDs. It doesn't mention how to handle the program_id case, but the other guidance is unambiguous.

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