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

Goes well beyond the annotations: describes the data source and sampling cadence (own check every 5 minutes), null semantics ('null when there were no checks, which is not 100%'), the unknown state and its reason, the full outage cause taxonomy, and what not_published/no_rdap means for domains. This is exactly the behavioral context an agent cannot get from readOnlyHint/idempotentHint.

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 answer (whether each site is up) and every clause carries information. However, it is one extremely dense run-on sentence with heavy parenthetical nesting, which hurts scannability for an agent parsing return-field lists.

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 fully specifies the return fields the agent will receive (state, uptime windows, answer time, outage lists, current outage, certificate, domain). Nothing an agent needs to interpret or safely report the result is missing.

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?

The schema already documents site_ids at 100% coverage including 'Omit for every site,' and the description largely repeats that ('Optional site_ids (default every site)'). It adds no format, limit, or ordering detail beyond the schema, so the high-coverage baseline of 3 applies.

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: per-site up/down state sourced from Royally's own 5-minute home-page checks, plus certificate and domain registration data. The scope and data sources are specific enough to distinguish it from siblings like speed_status, site_report, and backup_status.

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 it for client uptime figures' and adds a firm exclusion: 'never state uptime for a site this tool has no checks for.' It does not name the alternative sibling to use for other health metrics, so it stops short of full when/when-not/alternatives routing.

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