date_diff

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

With no annotations, the description carries full responsibility for behavioral disclosure. It mentions that the result includes multiple units, but it does not explain the output format (e.g., whether it returns an object with all units, a single choice, or a signed difference), the behavior when 'from' is later than 'to', or special handling of 'now'. This leaves significant behavioral gaps.

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 a single, tightly written sentence that delivers the core purpose and supported units without any filler. It is well-formatted and front-loaded with the primary action, making it easy to parse quickly.

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 is simple with only two parameters, all documented in the schema. However, the absence of an output schema and annotations means the description should at least indicate the return structure or notable behaviors. The current text states units but not how they are returned, leaving the description slightly incomplete for a tool that yields a multi-unit result.

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 schema provides 100% coverage with clear descriptions for both parameters ('Start date (ISO 8601 or now)' and 'End date (ISO 8601 or now)'). The description adds no additional parameter semantics beyond restating that there are two dates, so the baseline of 3 applies.

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 the action 'calculate the difference between two dates' with a specific resource (dates). It lists the output units (days, hours, minutes, seconds, weeks, business days), distinguishing it from sibling tools like business_days or date_math. The verb+resource structure leaves no ambiguity about the tool's purpose.

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 implies the tool should be used when needing a date difference, but provides no explicit comparison to alternatives like business_days or date_math. There is no mention of when-not-to-use or a recommended choice among siblings, so usage context is only implied.

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