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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description still adds real behavioral value: it clarifies no page is opened, describes which redirect mechanisms are followed, and discloses a concrete cost ($0.002 USDC per call via x402) that 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 dense sentence, front-loaded with the verb and resource, that efficiently packs the redirect scope, output contents, and cost without wasted phrasing.

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 steps in to enumerate the return values (redirect chain, final URL, cleaned URL, cross-domain flag), and it discloses the x402 payment requirement. Enough for an agent to call 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 description coverage is 0%, so the description carries the burden, and it does indicate the input is a short or tracking link. It still adds no format, scheme, or length guidance for the single url parameter, so it is helpful but not complete.

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 'Expand' plus resource 'short or tracking link', and it enumerates the outputs (redirect chain, final URL, clean URL, domain change) so the agent knows exactly what it returns. However, it never differentiates itself from close siblings like url_metadata or link, leaving that inference to the agent.

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?

The phrase 'without opening it' implies the safe, headless use case and hints at when to prefer this over a browser visit, but there is no explicit when-to-use, when-not, or named alternative. Usage context is implied rather than stated.

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