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

With no annotations, the description carries the full burden of explaining behavior. It does disclose that the tool returns true on a calendar-day match, but it does not explain date formats, timezone handling, the exact return type, or error behavior. The phrase 'Provide date or value' also suggests an input that the schema does not declare.

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 compact and front-loads the operation, but it contains a redundant 'Is Today:' prefix and the vague, unhelpful phrase 'or value.' These words do not earn their place and could mislead an agent.

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 zero-parameter tool with no output schema, the description should fully explain what the agent supplies and what it gets back. It partially explains the return condition, but it fails to reconcile the phantom input with the empty schema and omits format, timezone, and false/error behavior. An agent would not be able to invoke this tool correctly from the 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?

The input schema has zero properties, yet the description tells the agent to 'Provide date or value.' This is actively misleading: an agent cannot construct a valid call because no parameter is defined for the date. The description adds harmful meaning instead of clarifying the empty schema.

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: check whether a given date is today, returning a boolean. This is clear and not a tautology. It does not explicitly differentiate from sibling date predicates like x402-is-same-day or x402-is-past, but the core purpose is unambiguous.

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 alternatives such as is-same-day, is-future, is-past, is-weekend-date, or date-diff. 'Provide date or value' is a vague invocation hint, not usage guidance.

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