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

With no annotations, the description carries the full burden, yet it says nothing about accepted date formats, timezone handling, what happens on invalid input, or the shape of the result. The pricing line is the only behavior-adjacent detail and it concerns billing, not execution.

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?

Very short and front-loaded, which is good, but roughly half the text is a promotional free-trial blurb that adds nothing to correct invocation. The functional sentence wastes space by echoing the tool name.

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?

No annotations, no output schema, and zero parameter documentation mean the description must fill all gaps and does not. For a date-arithmetic tool with an unexplained "n" parameter, the agent lacks enough information to call it confidently.

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% across three parameters, and the description compensates for none of them. The parameter named "n" is completely opaque, and "date"/"days" get no format or type-guidance clarification (both are typed as strings with no hints).

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?

"Add Days: Add days to a date" does state a verb and a resource, but it is essentially a restatement of the tool name with no differentiation from close siblings such as x402-add-business-days, x402-add-hours, or x402-add-months. An agent cannot tell from the text which of those it should 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?

No when-to-use guidance, no prerequisites (e.g., date format expected), and no mention of the obvious alternatives. The only conditional text is a payment/trial note, which does not help tool selection.

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