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

With no annotations, the description carries the full burden of behavioral disclosure. It states the core action but does not mention return format, invalid-input behavior, redirect limits, network behavior, or whether any side effects occur.

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 short and front-loaded with the action. The redundant 'x402-url-expand:' prefix is unnecessary since it repeats the tool name, but the rest of the sentence is efficient and directly informative.

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 tool with no output schema and no annotations, the description should explain what the expanded result looks like, what input format is accepted, and how this differs from overlapping siblings such as x402-url-unshorten. It does none of these, leaving important gaps for an agent deciding how to call and interpret the 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 description coverage is 100%, so the structured schema already documents the only parameter. However, the schema description 'Short to process' is vague and does not clarify whether this should be a full URL, a short code, or something else. The tool description adds no additional parameter meaning.

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 uses a specific verb ('expand') with a clear resource ('shortened URLs') and the mechanism ('follow redirects'). It is understandable on its own, though it does not explicitly distinguish itself from the similar sibling x402-url-unshorten or x402-url-canonical.

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?

No guidance is provided on when to use this tool versus alternatives like x402-url-unshorten or x402-url-shorten. An agent is left to infer the appropriate context from the tool name and the generic description.

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