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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint, destructiveHint=false), so the bar is lower. The description still adds real behavior: a hard 15-hop cap, RFC 9110 §15.4 redirect semantics, loop detection, and the exact per-hop fields returned. It omits timeout/auth behavior and whether non-HTTP methods are followed, but that is a modest gap against strong annotation coverage.

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 sentences, zero filler. The core output contract is front-loaded and the standards reference is appended where it belongs rather than interrupting the primary statement.

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 carries the return-value burden and does so well by naming every reported hop field plus loop detection. What is missing is edge behavior (timeouts, non-2xx/3xx handling, request method), which leaves a small but real gap for a network-fetching tool.

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 50%: the url parameter is well documented with the SSRF-rejection caveat, but maxHops has no schema description. The description supplies the ceiling (max 15 hops), matching the schema maximum, but not the default of 10 or the per-call meaning of the parameter, so it only partially compensates.

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?

Specific verb+resource: it follows a URL through its redirect chain and enumerates exactly what is produced (per-hop URL, status, latency, Location; final URL; loop detection). An agent can distinguish this from check_url_status, which only reports terminal status, without opening either schema.

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?

Usage is implied by the purpose — you call it when you need to see intermediate hops rather than a single final status — but there is no explicit when-to-use/when-not and no named alternative among siblings like check_url_status or check_ssl. Guidance is sufficient to infer intent but never stated.

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