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

No annotations are provided, so the description carries the full burden. It discloses that 5 free trial calls per registered wallet are available, which is useful, but it says nothing about what operations are supported, how many calls are consumed per invocation, whether it mutates anything, what input formats are accepted, or what the response looks like. The behavior of the tool is essentially opaque.

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 short and front-loaded with the category, but it is under-specified rather than concise. The sentence 'Date arithmetic and formatting' is efficient, and the emoji plus trial note adds one useful piece of info, but the second sentence is promotional. There is almost no useful content, so it earns a 3 rather than higher.

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?

The tool has 12 optional string parameters, no output schema, no annotations, and a vague description. Given that complexity, the description is nowhere near sufficient. It doesn't enumerate valid operations, parameter combinations, date formats, or return behavior. An agent selecting among hundreds of date-related siblings cannot safely invoke this tool from this description alone.

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 100% but only in the vacuous sense: every parameter's description is just '<Name> to process'. These descriptions add no semantic meaning. The tool description doesn't clarify the parameters either. With 12 string parameters named generically (a, b, n, op, value, operation, date, days, months, epoch, start, end) and no meaningful guidance, an agent cannot know which combination to fill for a date-math operation. The description fails to compensate for the schema's emptiness.

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 says 'Date Math: Date arithmetic and formatting', which gives a broad category but no specific verb+resource. It doesn't distinguish from dozens of date siblings like x402-add-days, x402-date-diff, x402-parse-date, x402-format-date, or x402-epoch-to-date; the name 'x402-date-math' is equally generic. An agent cannot tell what specific operations it should invoke from this tool versus the many alternatives.

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 given about when to use this tool versus the numerous sibling date tools (add-days, date-diff, format-date, epoch-to-date, parse-date, days-between, etc.). The phrase 'Date arithmetic and formatting' implies coverage of date operations, but there is no explicit context, no exclusions, and no mention of which operations are supported. The only usage hint is the trial-call note, which is about billing, not about choosing the tool.

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