Set Zone

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

Annotations already flag this as a destructive, non-idempotent write, and the description adds real operational context beyond them: partial-update semantics ('only specified fields change'), create-vs-update field requirements, the immutability of the 'home' zone, and a concrete Claude Desktop 4-minute timeout/hang workaround. That last item is the kind of environment-specific behavior an agent could not infer from annotations.

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?

Front-loaded with purpose, then mode rules, then two compact examples, then the environment workaround. Every paragraph earns its place, though the Claude Desktop caveat paragraph is long relative to the core instruction and could be tightened.

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?

Covers both modes, create-time requirements, defaults (radius/passive documented in schema), and the special-case zone. An output schema exists, so return values need no explanation. Missing only failure behavior (e.g., duplicate name, invalid coordinates), which is a modest gap for a create-or-update 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, but the description adds meaning the schema cannot express: the schema declares ZERO required parameters, while the description tells the agent that name, latitude and longitude are required on create. It also pairs the update path with concrete example payloads (radius=200) showing partial updates are legal.

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 pair and resource ('Create or update a Home Assistant zone') and immediately clarifies the two operating modes. It also names the sibling it is not ('The home zone ... cannot be modified here'), letting an agent distinguish it from ha_get_zone/ha_remove_zone without opening a schema.

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 conditional routing: omit zone_id to create (with which fields become required), supply zone_id to update with partial-field semantics. It also states an exclusion (the 'home' zone is YAML-defined). It stops short of naming the concrete alternatives (ha_get_zone for lookup, ha_remove_zone for deletion) in the description body itself.

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