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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so the bar is lower. The description adds valuable behavioral details: it traces the full redirect chain and reports per-hop status codes, response times, and the final destination, which 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?

A single, information-dense sentence that conveys the tool's function, output, and access model with zero redundancy. Every word contributes value.

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 simple one-parameter tool with robust annotations and no output schema, the description sufficiently explains what the tool does, what it returns, and the access model. No additional context is needed.

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% for the single 'url' parameter, described as 'Starting URL' with URI format. The description doesn't add additional meaning beyond the schema, but none is needed for a single obvious parameter. 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 clearly states the verb ('Follow') and resource ('a URL's redirect chain'), and specifies the output (every hop with status code, response time, final destination). This distinctly separates it from sibling tools like DNS lookups or website status checkers.

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?

Describes the tool's specific use case (following redirect chains) and notes it's a 'Free public API', implying no authentication barrier. It doesn't explicitly state when not to use it, but the context is clear enough given the sibling tool names.

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