List services

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context beyond that: the unscoped call returns all domains with service names, while the scoped call returns fields/parameters — a meaningful disclosure of return shape in the absence of an output schema.

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 core action, then the two return modes. Every clause earns its place with zero filler.

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 no output schema, the description carries the burden of describing return shape and does so for both modes, plus connects to ha_call_service. Minor gap: it does not cover the instance_id guard behavior, though the schema already documents it.

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 clarifying semantics for domain (unscoped = all domains, scoped = fields/parameters) and implies the purpose of the fields an agent will receive. The instance_id parameter's behavior is left entirely to the schema.

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?

Specific verb ('List') plus resource ('callable Home Assistant services'), with the two return modes spelled out. It is clearly distinguishable from siblings like ha_list_entities or ha_get_config, and it names the downstream tool it feeds (ha_call_service).

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?

Explains the two usage modes (no domain vs. with domain) and ties the domain mode to needing field/parameter details before calling ha_call_service. It does not state when to prefer a sibling or any exclusions, so it stops short of explicit when-not guidance.

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