set_hvac_mode

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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the safety profile is covered. The description adds genuinely new context by spelling out the two authentication paths required to complete the write, which the annotations cannot express. It stops short of explaining reversibility or effects on the running schedule.

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 sentences, zero filler, with the action and its allowed values front-loaded before the permission requirements. Every clause carries information the agent needs.

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 a two-parameter mutation tool whose annotations already disclose the destructive/non-idempotent profile, the description covers the action, the value set, and the auth gate. Nothing critical is missing, though a note about interaction with an active schedule or the effect on temperature setpoints would round it out.

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 50%: thermostat_id is documented in the schema while mode is defined only by its enum. The description restates the enum values, which duplicates the schema rather than adding format or constraint detail, so the baseline 3 is appropriate.

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 (Change) and resource (thermostat HVAC mode) and enumerates the exact resulting states (off, heat, cool, auto). An agent can distinguish this from set_temperature and resume_schedule without opening any schema, since the mode-setting action is uniquely named.

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 supplies prerequisites (account write permission, client write scope, or --allow-writes locally) but never says when to choose this over set_temperature or resume_schedule. Usage is implied by the enumerated modes rather than stated as guidance, so it sits at the minimum-viable level.

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