List entity groups

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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds real context beyond that: the underlying data source (ha.get_states()), the filtering rule, and the exact per-group fields returned, which tells the agent the data is a point-in-time state snapshot rather than a registry lookup.

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 the purpose, followed by implementation and return shape in a compact three-part structure. The 'Returns:' field list is slightly redundant against the existing output schema, which keeps it from a 5.

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 parameterless read-only listing tool with an output schema and full annotation coverage, the description supplies everything an agent needs: what is listed, where the data comes from, how it is filtered, and the shape of each item.

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?

Zero parameters, and the input schema is a closed empty object, so there is nothing to disambiguate. Baseline for a parameterless tool is 4; the description correctly implies no arguments are accepted.

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 and resource ('List all Home Assistant entity groups') and narrows scope precisely with '(group.* entities)', which separates it from the broad entities_list_entities sibling. It does not explicitly name a sibling to route away from, so it falls just short of a 5.

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?

Usage is implied rather than stated: by explaining that it reads ha.get_states() and keeps group.* entries, it signals 'use this instead of scanning all states yourself.' There is no explicit when-to-use, when-not-to-use, or named alternative (e.g. entities_list_entities).

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