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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false; the description adds real value on top by specifying exactly what is destroyed ("Replaces an earlier layout on those faces") and how to recover it, and by disclosing the return values and that the call costs no points. It stops short of saying what happens when no qualifying roof face 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?

The primary action is front-loaded in the first sentence, and each subsequent sentence carries a distinct fact (remove mode, undo path, not-a-forecast caveat, point cost). The first sentence is heavily loaded with qualifiers, which slightly hurts readability.

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?

With no output schema, the description correctly supplies the return shape (module count, area, rated power in kWp), and annotations plus text cover the destructive/idempotent profile. Remaining gaps are edge-case behavior (no qualifying faces, interaction with existing non-solar geometry) rather than anything blocking a correct call.

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 coverage is 100%, so the baseline is 3, but the description adds behavioral meaning the schema does not: it explains that the same tool has a removal mode ("Or removes them") and ties the kind enum to the physical resource being laid out. The language parameter and the south vs. eastWest distinction are left entirely to the schema.

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 states a specific verb and resource ("Lays out photovoltaic modules... on every roof face") plus the placement rule (non-north faces, edge margins, racks on flat roofs) and the return payload. The clause "A layout, not a yield forecast" cleanly separates it from vedutum_sun_and_shadow without needing either schema.

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 context is clear: it applies to roof faces not facing north and defaults to a south-facing rack layout on flat roofs. It names vedutum_undo_last_change as the revert path, but gives no explicit "use this instead when..." routing against siblings such as vedutum_set_design or vedutum_sun_and_shadow.

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