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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds real value on top: what comes back (live status, 90-day uptime percent from PingDeck checks, recent incidents), the coverage scope (61 services), and that no account or API key is required — an auth fact the annotations do not convey.

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?

Opens with the core purpose, then examples, then return content, then the zero-argument behavior and auth note. Every sentence carries a distinct fact and the ordering is front-loaded with the decision-relevant information.

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-required-parameter read tool with no output schema, the description covers purpose, return contents, scope limits and auth requirements — everything an agent needs before calling. No material gap remains.

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?

Schema coverage is 100% and the single parameter already documents that name, slug or domain are accepted and that omitting it lists all services. The description restates the omit-to-list behavior and gives example values, adding marginal meaning beyond the schema, so baseline 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 (check) and resource (a popular online service) plus the crucial qualifier 'down for everyone', which distinguishes it from single-site checks like check_website. The example list (ChatGPT, WhatsApp, Discord...) removes ambiguity about what counts as a 'popular service'.

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 an explicit calling pattern for the degenerate case ('Call the tool with no service to get the list'), which is the main usage ambiguity for a 1-optional-param tool. It does not name a sibling such as check_website or check_ssl or state when to prefer them, so it stops 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.