date_math

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

With no annotations, the description carries the full burden. It discloses an important behavioral nuance: days are calendar-based and DST-safe while hours and minutes are absolute, and it notes that diff can handle two different zones. However, it does not specify the output format/unit for diff, which is a minor gap.

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?

One dense but well-structured sentence that front-loads the tool's purpose and packs in key clarifications with parentheticals. No wasted words.

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 no output schema, and the description does not state what the return looks like (e.g., a datetime for add, or a duration unit for diff). It covers the operation semantics well but leaves the output contract underspecified for a moderate-complexity tool.

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 baseline is 3. The description adds value by explaining how unit semantics work (calendar days vs absolute hours/minutes), which is not in the schema's enum listing.

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 clearly states 'Timezone-aware date arithmetic: add or subtract a duration to a datetime... or compute the difference between two datetimes' – a specific verb and resource, and it distinguishes itself from sibling conversion/current-time tools by focusing on arithmetic.

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?

It clearly describes the operations (add/subtract/diff) and the context of timezone-awareness, but does not explicitly name alternatives or when-not-to-use cases. The scope is clear enough, yet no exclusions are mentioned.

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