ha_call_service

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

Annotations already flag destructiveHint=true and openWorldHint=true, so the safety profile is known. The description adds real value beyond that: 'Acts on the real home' reinforces the live side effect, and the confirm=false dry-run pattern is essential behavioral guidance not derivable from annotations alone.

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 tight sentences, front-loaded with the action and followed by the safety constraint. The 'e.g. to test what a key will do' clause earns its place as a concrete use case, though it is somewhat narrow.

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?

An output schema exists so return values need not be explained, and annotations carry the safety profile. Combined with the description's dry-run guidance, an agent has what it needs, though the undocumented entity_id and lack of sibling routing leave minor gaps.

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 75% (service, data, confirm documented; entity_id bare). The description adds no syntax or format detail beyond what the schema provides, only restating the confirm workflow already in the schema. 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+resource ('Call a Home Assistant service') and gives a concrete example use ('test what a key will do'). It is clearly distinct from read-only siblings like ha_search or ha_describe_entity, though it does not explicitly name those alternatives.

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?

Provides a clear workflow: call with confirm=false first, get the user's OK, then call for real. This tells the agent when and how to invoke it safely. It lacks explicit when-not conditions or named sibling alternatives, so it stops short of a 5.

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