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

No annotations are provided, so the description must carry the full behavioral burden. It does disclose the comparison basis ('relative to now'), but it omits the return type, handling of equality/boundary cases, timezone assumptions, and how the date/timestamp is actually received. The implied input also conflicts with the empty schema, making the behavior unclear.

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 two concise sentences with the core action and use case front-loaded. The only minor flaw is the redundant 'Is Past:' prefix, which repeats the tool name and adds no information.

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 parameter schema entries, the description leaves a critical gap: it promises an input that the schema does not define, so the agent cannot know how to invoke the tool correctly. It also lacks edge-case behavior like whether the current moment counts as past or what happens with invalid date formats.

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 parameters, so there is nothing for the description to document; the baseline is 4. However, the description explicitly mentions 'a given date or timestamp' as if such an input exists, which is contradicted by the empty schema. This actively misleads rather than adding useful parameter 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 states a specific predicate: check whether a given date or timestamp is in the past relative to now. It also names a concrete use case ('deadline or expiry checks'). However, it does not explicitly differentiate itself from inverse or related sibling tools like x402-is-future.

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?

The description gives a clear context ('deadline or expiry checks') but provides no exclusions or alternative tool guidance. More importantly, it says a date/timestamp is 'given' while the input schema defines zero parameters, so an agent cannot tell how to supply the input or when this tool should be chosen over siblings.

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