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

Beyond the annotations, the description discloses key behavior: it never runs the check or pays, the base price is $0.003, payment is USDC on Base only, the x402 v2 flow uses GET with an email query, no SMTP connection is made, and bad input or DNS failure is not charged.

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 purpose and price are front-loaded, followed by payment mechanics and relevant caveats. There is some repetition, notably 'one address per call' and 'USDC on Base only,' but the content remains focused.

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 zero-parameter quote tool with rich annotations and no output schema, the description covers the return purpose, price, payment protocol, underlying check capabilities, and charge conditions. An agent has enough information to understand what this tool does and does not do.

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?

The tool takes zero MCP parameters, so the baseline is 4. The description explains that the email address is supplied in the underlying HTTP payment call rather than as an argument to this tool, which helps prevent confusion.

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: it returns payment terms for the email check endpoint. It also immediately distinguishes itself from the actual check by saying it never runs the check or pays.

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 gives clear context that this tool is for retrieving payment terms before paying over HTTP with x402 v2, and it explicitly says it never runs the check or pays. It does not name a specific sibling alternative for performing the check, so it falls short of a 5.

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