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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is fully covered. The description adds only a mild diagnostic framing ("reachable") and says nothing about what a negative result implies or any rate/latency considerations; an output schema exists, so return values need no explanation here.

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, with the core action and audience front-loaded and the scope exclusion following immediately. Nothing is repeated from the title or annotations.

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-argument health probe with full annotation coverage and an output schema, this covers the essentials: who it is for, what it verifies, and what it does not do. Only a hint about how to react to a failure would make it exhaustive.

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 the baseline is 4. The description does not need to describe inputs, and it correctly does not invent any.

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 — check that the iter0 API and its developer contracts are reachable — and narrows the audience to developers integrating the API. The negative clause ("Does not build or edit websites") makes it clearly distinct from the site-building siblings, though "developer contracts" is left somewhat abstract.

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?

Gives a clear context for use (developer integration / reachability verification) and an explicit exclusion that rules out the build/edit siblings. It does not name a specific alternative tool for diagnosing a failed check, so it stops just short of full when/when-not guidance.

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