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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds that the tool quantifies lag magnitude, implying a diagnostic read, but says nothing about response shape, units (blocks/time), or thresholds for 'healthy'. Some added value, not rich.

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 short sentences, the measurement is front-loaded and the usage cue follows immediately. No filler or restatement of the title.

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 parameters and no output schema, the description carries a light burden: what the tool measures and when to reach for it, both of which are present. It could note the units or that a healthy result is near-zero, but the omission is minor for a zero-arg diagnostic.

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 tool takes zero parameters, so there are no parameter semantics to document. Baseline 4 applies; the description does not need to compensate for anything in 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?

The description names a precise quantity — the lag between the ArcID indexer and the Arc chain head — so an agent knows exactly what this tool measures. It lacks an explicit verb (e.g. 'report' or 'return'), but the resource and scope are unambiguous. No sibling tool is health-related, so differentiation is not a concern.

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?

'Check this when results look empty or stale' gives a concrete triggering condition rather than generic advice. There are no when-not clauses or named alternatives, but none of the sibling tools (search_agents, get_agent, get_registry_stats) overlap enough to require routing guidance.

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