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

Annotations cover the safety profile (readOnly, idempotent, openWorld, non-destructive), but the description adds genuinely important behavior: the x402/MPP payment flow, the $0.10 per-call cost, that checks run from Cloudflare's edge, and critically that 'Bad input is refused before any charge' — a cost-safety guarantee not implied by any annotation.

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 usage trigger and the sibling routing, and each sentence carries real information (checks performed, payment mechanics, cost, error behavior). The middle sentence packing endpoint, price, schema, example, and client instructions into one clause is dense but justified.

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 still tells the agent exactly what comes back (the paid x402 request body plus response schema and example) and how to obtain the data. Payment flow, cost, error handling, and the single-URL alternative are all covered.

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 is already documented ('1 to 10 URLs; duplicates are removed'), so the baseline is 3. The description adds only the http(s) scheme constraint and restates the 10-URL cap; it does not clarify what counts as 'bad input' that triggers the pre-charge refusal.

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 (batch uptime ping), the scope (up to 10 http(s) URLs in one POST), what each check covers (status, latency, redirects, TLS, server), and explicitly names the single-URL sibling it is not: 'For one URL use url_uptime_ping.'

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?

Opens with the explicit trigger ('Use when you monitor several endpoints') and closes with the alternative and its selection condition ('For one URL use url_uptime_ping'). Both the when-to-use and the when-to-use-something-else cases are covered.

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