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, but it only states the basic operation. It does not specify the output representation (e.g., 0-6 vs 1-7 vs 'Monday'), accepted date formats, timezone handling, or behavior for invalid dates.

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 extremely compact: one substantive sentence. The leading 'Day Of Week:' label is redundant with the tool name and is minor waste, but overall the structure is efficient and easy to parse.

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 is incomplete: it never states what the returned day of week looks like or what date formats are accepted. Among dozens of date-related siblings, this ambiguity makes reliable invocation and interpretation harder.

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 only parameter 'date' has a schema description ('Date to process'), giving 100% coverage, so the baseline is 3. The free-text description adds no additional format, constraint, or example to help the agent construct a valid value.

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 clear verb ('Get') and resource ('the day of week for a date'). It is distinct from nearby siblings like x402-day-of-year and x402-day-name-full because it names day-of-week specifically, though it leaves ambiguous whether the result is numeric or textual.

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 about when to use this tool versus alternatives such as x402-day-name-full, x402-day-name-short, or x402-week-number. There are no exclusions, alternative references, or context cues beyond the tool name itself.

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