List available services

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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds useful implementation detail: it calls ha.list_services() via HTTP GET /api/services and filters client-side, which tells the agent how freshness and filtering work. It does not cover auth or rate limits.

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-loads the purpose and then adds implementation, usage, and return shape in labeled sentences. It is tight and scannable, though the explicit return description is mildly redundant given the existing output schema.

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?

Complete for a simple list tool: purpose, usage context, mechanism, and return format are all covered. Annotations and the output schema supply safety and structure, leaving no critical gap for correct invocation.

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 100%, so the domain parameter and its omission behavior are already documented. The description adds that filtering is performed client-side, a semantic detail beyond the schema that clarifies what the parameter actually does.

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 ('List') and resource ('services'), including scope ('all services Home Assistant currently has registered') and optional domain filtering. It distinguishes itself from sibling services_call_service by framing this as discovery before calling a 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?

Explicitly says 'Use when: discovering which services and fields a domain supports before calling services_call_service.' This names the alternative tool and the condition that selects it, giving the agent clear routing guidance.

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