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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds real value by disclosing what the computation returns (Q in kWh, E_el in kWh, t in h) — important because there is no output schema. It does not mention assumptions (e.g. no heat losses, constant efficiency), which would have earned a 5.

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, zero filler, purpose front-loaded before the result list. Every clause earns its place.

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 an all-optional calculator with full schema coverage and no output schema, the description supplies the missing return-value information. What is missing is any statement of the model's assumptions or the relationship between the PV-surplus scenario and the given inputs.

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 titles, units, ranges and defaults on every parameter, so the schema carries the semantics. The description adds nothing about how T1/T2/eta/P_el/V feed the formulas, and the mention of PV surplus does not map to any actual parameter, leaving that reference unanchored. Baseline 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?

Names a specific verb ("Berechnen") and a precisely scoped resource: heating time and electricity consumption of a heating rod in a hot water tank. It even enumerates the three output quantities with units. Differentiation from siblings is impossible because every sibling is an opaque bot_XXX identifier, so this is the ceiling for the definition alone.

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?

"auch bei PV-Überschuss" hints at the PV-surplus sizing scenario, but there is no explicit when-to-use/when-not, no prerequisites, and no named alternative among the 30+ siblings. Usage is only implied by the topic.

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