Check HA API reachability

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 non-obvious behavior: `ha.ping()` catches connection errors internally and reports plain reachability rather than health, which is genuine context beyond the 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 the core definition, then cleanly segmented into 'Use when', 'Not for', and 'Returns'. Every sentence carries information; no 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?

For a zero-parameter liveness probe with full annotation coverage and an output schema, the description supplies everything needed: scope, alternatives, and a note on what the result does and does not represent.

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, so per the rubric the baseline is 4. The description additionally documents the return shape (`{reachable, url}` with the configured HA_URL), though with no inputs there is no parameter semantics to add.

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 (check) and resource (HA API reachability over HTTP) and even names the underlying call (`GET /api/` via `ha.ping()`). It distinguishes itself from `history_get_system_info`, `history_get_ha_config`, and `system_get_system_health` without the agent needing to open any 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?

Explicit 'Use when' (confirming HA is up before other calls, liveness probing) and 'Not for' clauses route the agent to the correct alternative for raw payload, config, and subsystem health. Nothing is left to inference.

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