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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the agent knows this is a safe, self-contained computation. The description adds the useful fact that this is a pure calculation whose result is the three named quantities, which partially compensates for the absent output schema, but it discloses nothing about units, assumptions, or failure behavior beyond that.

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 short bilingual sentences, front-loaded with the purpose and immediately followed by the same statement in English. Nothing is wasted and no sentence is redundant.

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 10-parameter calculator with full schema coverage and no output schema, the description supplies the essential missing piece — what the calculation returns. It stops short of clarifying the mode-dependent parameter split and the template-vs-appliances relationship, but the schema covers those.

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% and each parameter (mode, panelW, sunHours, template, appliances, backupHours, autonomyDays, concurrencyPct) already carries a Persian explanation, including mode-specific applicability. The description adds no parameter-level meaning beyond the schema, so the 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?

The description names a specific verb (calculate) and enumerates the concrete outputs — battery capacity, inverter power, solar panel count — and scopes them to backup or off-grid systems. It is far clearer than a tautology, but it does not differentiate itself from the related sibling list_load_templates, which supplies the preset templates the 'template' parameter consumes.

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?

It states the domain context ('backup or off-grid') and that input can come from a load list or peak load, which implies usage. However, it never says when to choose this tool over list_load_templates, nor that templates should be fetched first, and gives no exclusions or prerequisites.

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