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

No annotations are supplied, so the description carries the full burden. It does disclose the output domain ('week of year (1-53)') and a pricing/trial condition ('5 free trial calls per signed wallet'), which is real behavioral context. It does not say whether the operation is a pure read, what timezone or week-numbering convention applies at year boundaries, or how an invalid date is handled.

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 front-loaded with the purpose and output range in two short sentences with no redundancy. The trailing promotional line about free trial calls is not needed for tool selection, but it is short and does not obscure the main statement.

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 read-only calculation with no output schema, the description covers purpose and return range adequately. It falls short on the two things an agent actually needs to invoke it correctly: the accepted date format and the default behavior when no date is supplied.

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% for the single 'date' parameter, so the description must compensate and it largely does not. 'Provide date' restates the field name without specifying the expected format (ISO 8601 string, YYYY-MM-DD, timestamp?) or what value is assumed when the parameter is absent, which matters since required parameters is 0.

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: 'Calculate the ISO 8601 week number for a given date', which is unambiguous about what the tool returns. However, it does not distinguish itself from closely named siblings such as x402-week-number, x402-week-of-year, and x402-calendar-weeks, so an agent cannot tell from the description which of these to pick.

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 only usage cue is 'Provide date' and the output range. There is no statement of when to prefer this over x402-week-number or x402-week-of-year, no prerequisites, and no note on what happens if the optional date is omitted.

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