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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses nothing: no return format, no semantics of 'between' (inclusive/exclusive), no date format expectations, no edge cases. The description is entirely uninformative about how the tool behaves.

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 short but wastes its only content on repetition of the tool name. This is under-specification rather than effective conciseness; a useful description would earn its brevity by packing in distinguishing details.

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 2-parameter tool with no annotations and no output schema, the description is completely inadequate. It fails to specify input date formats, return value, or how it differs from similar date tools. An agent cannot reliably select or invoke this tool based on this definition.

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%, so the baseline is 3 even though the description adds no parameter information. The schema's own descriptions ('End to process', 'Start to process') are barely more explanatory than the parameter names, but the names start/end combined with the tool name provide moderate meaning.

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 'Days Between: Days Between' is a pure tautology that merely restates the tool name. It provides no verb, resource, or scope beyond what the name already implies, and does nothing to distinguish this tool from closely related siblings like x402-date-diff, x402-days-since, or x402-days-until.

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?

There is no guidance whatsoever about when to use this tool versus the many date-related alternatives in the sibling list. The description contains no context, no exclusions, and no mention of alternatives, leaving the agent to guess when days-between is the right choice.

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