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

Annotations already declare readOnlyHint=true and idempotentHint=true, indicating safe, pure calculation. The description adds the core calculation logic (how the depreciable base is allocated), but does not disclose potential edge cases such as what happens when unitsThisPeriod exceeds remaining units, or how salvage value is handled in the formula. It provides minimal additional behavioral context beyond the annotations.

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 description is a single concise sentence that front-loads the tool name and provides the essential calculation concept in a structured, readable way. There is zero wasted wording; every part contributes to understanding the tool's function.

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 simple calculator with complete parameter descriptions and an output schema, the description explains the core method sufficiently. It lacks usage guidance relative to sibling depreciation tools, but that is more of a usage-guideline concern. Given the annotations and output schema, the description is complete enough for an agent to invoke the tool correctly for standard calculations.

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?

All four parameters are already described in the schema (100% coverage): value, salvage, totalUnits, unitsThisPeriod. The description uses 'depreciable base' to imply value minus salvage, and 'units used this period' maps to unitsThisPeriod, but it does not add new semantics or clarify units or formula syntax beyond the schema descriptions. Baseline 3 is appropriate given full schema coverage.

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 clearly explains the tool's purpose: it computes units-of-production depreciation by spreading the depreciable base over total expected units and charging based on units used this period. It uses a specific method name and distinguishes itself from time-based methods like straight-line depreciation through the unit-based allocation concept.

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?

The description provides no guidance on when to use this tool versus alternative depreciation methods (e.g., straight-line, declining-balance) or other financial tools. It does not mention scenarios where units-of-production is appropriate (e.g., usage-based assets) or any exclusions. The implied usage is only that it's a depreciation calculator, but no differentiation from siblings is given.

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