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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It reveals the operation is a pure calculation returning a 1-53 value, but omits the required input date format, timezone handling, invalid-date behavior, and the exact structure of the returned value. For a tool with zero annotation coverage, this is a significant gap.

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?

Two compact sentences with the purpose and verb front-loaded before the instruction sentence. The 'ISO Week:' prefix is mildly redundant with the tool name but compensates for the null title; there is minimal wasted text.

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, no annotations, and an empty input schema, the description is the sole source of guidance, yet it fails to specify how to supply the date it expressly requires. An agent cannot reliably invoke this tool correctly based on the available information.

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 schema declares zero parameters while the description instructs 'Provide date' — an agent has no mechanism for passing the date since no parameter is defined. The description adds the semantic that a date is required but contradicts the empty schema rather than clarifying how the input is supplied, which actively undermines correct invocation.

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' with an explicit output range ('week of year (1-53)'). The 'ISO 8601' qualifier differentiates it from siblings like x402-week-number and x402-week-of-year, though those alternatives are not named.

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?

Usage is implied — an agent can reasonably infer to use this tool when an ISO 8601 week number is needed. However, with very close siblings (x402-week-number, x402-week-of-year, x402-calendar-weeks), no explicit when/when-not guidance or alternative routing is given, leaving tool selection to inference.

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