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

Annotations already declare readOnlyHint, idempotentHint and a closed-world scope, so the safety profile is covered. The description adds real value by enumerating the exact result quantities (ΔU [V], ΔU [%], ΔP [W], minimum cross-section, recommended standard cross-section) and the design rule (ΔU ≤ 1 %, min. 4 mm²) that underlies the output — useful since no output schema exists.

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?

Two sentences, front-loaded with the calculation purpose followed by the result list; no filler. The output enumeration is somewhat list-heavy but earns its place given there is no output schema.

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?

All five parameters are optional with defaults and fully documented in the schema, and the description compensates for the absent output schema by naming every returned value. What remains missing is context on domain assumptions (one-way vs round-trip length, applicability limits) and the absence of sibling routing, which keeps it short of a 5.

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 % — every parameter carries a title, unit, range and the region enum is explained in the schema itself. The description adds no parameter-level information (e.g. it does not clarify that 'laenge' is one-way length and gets doubled, nor how region changes the standard applied). Baseline 3 applies when the schema does the work.

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 calculation domain: voltage drop, relative voltage drop, power loss and minimum conductor cross-section for a DC solar cable, citing VDE 0100-712. An agent knows exactly what computation this performs. It cannot distinguish from siblings, but the siblings are anonymized bot_XXX names with no semantics to differentiate against, so no penalty beyond the missing comparison.

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 only implied by the subject matter — an agent infers this is for PV string cable sizing, but the description never states when to use it, when another tool is preferable, or any prerequisites (e.g. that lengths are one-way, or that region selects the applicable standard). No exclusions are offered.

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