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

With no annotations, the description carries the full behavioral burden and does so thoroughly: it discloses redirect handling (max 4), the response fields, the single-URL limit, the short timeout, the blocking of private addresses, and the non-throwing error behavior for unreachable hosts. It also notes the service is free and anonymous.

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?

The description is compact and every sentence adds value: the first sentence states purpose and outputs, the second covers constraints and error behavior, and the third gives a concrete example. It is well-structured and front-loaded with the most 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 single-parameter tool with no output schema, the description is unusually complete: it covers input constraints, redirect behavior, timeout behavior, output fields, error semantics, cost/anonymity, and an example. An agent has everything needed to invoke and interpret the result correctly.

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%, so the baseline is 3, but the description adds meaningful value beyond the schema: it clarifies the URL must be public http(s), provides a concrete example URL, and explains what the call returns for that example. This gives an agent more operational context than the schema alone.

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 (probe) and resource (a public URL endpoint), and enumerates what it reports: final URL, HTTP status, latency, and content type. This clearly differentiates it as a liveness/health-check tool distinct from the sibling tools.

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 it is for public URLs, blocks private/internal addresses, and that each call probes exactly one URL with a short timeout. It also notes unreachable hosts return a structured error rather than throwing, giving clear call expectations, though it does not explicitly name alternative tools for other use cases.

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