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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 only states the basic calculation direction, but does not mention output format (e.g., days, milliseconds, human-readable), timezone handling, or any edge cases (e.g., past vs future targets). This lack of detail leaves significant ambiguity for an agent invoking the tool.

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, concise sentence that is front-loaded with the key action ('Calculate time remaining') and efficiently communicates the tool's dual purpose. There is no redundant or filler content.

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, but due to the absence of an output schema and annotations, the description should have explained what the tool returns (e.g., duration unit, format). It does not, leaving a significant gap. The mention of 'from' as optional reference is not in the description, further limiting completeness for non-default usage.

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%, with clear descriptions for both parameters ('Reference date (default: now)' and 'Target date (ISO 8601)'). The tool description adds minimal value beyond the schema, only implying the relationship between target and from. Since the schema already documents parameters well, a baseline of 3 is appropriate.

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 tool's function: calculate time remaining or elapsed relative to a target date. It uses a specific verb ('Calculate') and resource ('time remaining... target date'). While it doesn't explicitly distinguish itself from sibling tools like date_diff, the focus on 'until' and 'since' implies a reference to now, providing moderate differentiation.

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 provided on when to use this tool versus alternatives. The description does not mention sibling tools or scenarios where date_diff or formatters would be preferred. The usage context is implied by the tool's name and basic function, but not explicit.

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