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

With no annotations provided, the description fully carries the behavioral burden. It discloses the one-hop iteration behavior, the 10-hop limit, refusal to follow redirects into private address space, and the per-call cost via x402 on Base. This is far beyond minimal and gives the agent realistic expectations.

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?

Three sentences pack the purpose, output details, usage guidance, safety limits, and cost without redundancy. The most important behavior is front-loaded, and every clause earns its place.

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 and no annotations, the description is remarkably complete: it explains what the result contains, how far it will go, what it refuses to do, and what it costs. An agent has enough context to select the tool and interpret its results.

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 lone 'url' parameter is already described with an example. The description adds contextual color about shortened/tracked/unfamiliar links, but does not materially extend the parameter semantics beyond what the schema provides, so baseline 3 is appropriate.

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?

The description states a precise operation—following a URL's redirect chain hop by hop and reporting each step—along with the specific outputs (intermediate host/status, final destination, cross-host flag, cleaned URL). This clearly distinguishes it from siblings like url_headers, which inspects headers rather than resolving redirects.

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?

It explicitly says to use the tool before following or showing a shortened, tracked, or unfamiliar link, and notes that a shortener cannot hide its destination. It does not explicitly name alternative tools or exclusion cases, but the use context is clear.

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