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

With no annotations, the description carries the full behavioral burden. It discloses the output format and the default reference time, which is useful, but it omits timezone handling, invalid input behavior, and parsing expectations for the datetime string.

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, well-structured sentence that front-loads the core behavior and includes brief examples. Every element earns its place, with no redundant or vague phrasing.

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 simple utility with no annotations and no output schema, the description explains the return shape via examples and clarifies the default reference. However, it leaves the datetime input format and timezone behavior unspecified, which are important for correct invocation.

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 0%, so the description must compensate, but it only clarifies that 'reference' defaults to now and that the operation compares datetime to reference. The required 'datetime' parameter's accepted format or syntax is never explained, leaving a significant gap for an agent trying to invoke the tool.

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 transformation with concrete output examples ('2 hours ago', 'in 3 days'), making the tool's purpose immediately understandable. It does not explicitly differentiate itself from siblings like time_between or time_format, so it falls short of a 5.

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?

Usage is implied by the tool's purpose and the note that reference defaults to now, but there is no explicit guidance on when to choose this over time_between, time_format, or time_parse. The description gives context for calling it but does not mention exclusions or alternatives.

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