Set System Units

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

No annotations are provided, so the description carries the full behavioral burden. It says nothing about whether changing lens units merely relabels values or rescales existing prescription data, whether it requires an active connection/open file, or whether the change is reversible. For a system-wide mutation in an optical design context, this is a significant 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 short, front-loaded sentence with no filler or redundancy. It is appropriately sized for a single-parameter tool, though it is arguably too terse to earn a top score.

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?

Given no annotations and no output schema, the description should at minimum state the effect on existing system data and any connection/precondition requirements. With only one well-documented parameter, the core invocation is clear, but the behavioral context is under-specified for a system-level mutation.

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% - the single lensUnits parameter is documented with an enum and a description ('Lens coordinate and prescription units'). The description adds no additional meaning beyond the schema, which matches the baseline 3 when the schema does the heavy lifting.

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 names a specific verb ('Set') and resource ('the current optical system's lens units'), so the action is unambiguous. It implicitly distinguishes itself from the sibling zemax_get_system_units via the set/get verb pair, but does not explicitly call out that contrast or differentiate from zemax_set_mtf_units, which also sets units of a different kind.

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?

There is no statement of when to use this tool, no prerequisites (e.g., whether a system must be open or connected first), and no mention of alternatives such as zemax_set_mtf_units or zemax_get_system_units. The agent must infer all usage context.

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