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

No annotations are provided, so the description carries the full behavioral burden. It discloses the free-trial limit ('5 free trial calls per signed wallet'), which is useful, but it does not describe the return format, whether results are deduplicated, how invalid addresses are handled, or what happens after the trial calls are exhausted.

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 definition is short and front-loaded with the core action. The payment/trial sentence is extra but brief, and there is no unnecessary exposition.

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 extraction tool with no output schema, the core purpose is covered. Still, an agent would benefit from knowing the return shape and trial/paid behavior, which are omitted.

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?

There is one parameter named 'text', and the description references extracting from text, so the mapping is reasonably obvious. However, schema description coverage is 0%, and the description adds no detail about input format, size limits, or whether the text can contain multiple addresses.

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 specific verb and resource: 'Extract email addresses from text.' That is clearer than a tautology and distinguishes the tool from general text utilities, though it does not explicitly differentiate it from nearby siblings such as x402-extract-urls or x402-extract-numbers.

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 implies the basic use case by saying emails are extracted from text, but it gives no when-to-use guidance, no when-not-to-use guidance, and no alternatives such as validation or masking tools. The free-trial note is commercial context, not usage guidance.

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