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

With no annotations, the description carries the behavioral burden. It discloses the output format (USD and CAD amounts plus fine metal weight) and clarifies ambiguous semantics like 'oz = avoirdupois ounces — postal-scale ounces' and purity fraction meanings. It does not mention reliance on live spot prices or rounding behavior, but for a calculator this is adequate.

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?

Three sentences with no filler: the first states purpose, the second states what is returned, the third clarifies parameter semantics. The most critical information is front-loaded and every sentence contributes.

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 4-parameter calculator with no output schema, the description is nearly complete: it explains the purpose, all parameter meanings, example purities, and output values. The only missing elements are an explicit pointer to calculate_coin_melt for coin-specific cases and a note on the spot-price source, but these are minor for a competent agent.

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. The description adds meaningful value beyond the schema by giving concrete purity examples (0.925 sterling, 0.999 fine, 0.9 US coin silver) and disambiguating the unit 'oz' as avoirdupois postal-scale ounces, which is not evident from the enum alone.

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 opens with a specific verb and resource: 'Calculate the melt value (intrinsic bullion value) of silver or gold from weight and purity.' The examples (sterling silver flatware, .999 rounds, scrap gold) further clarify scope and distinguish it from siblings like calculate_coin_melt (coin-specific) and get_spot_price (price lookup).

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 establishes clear applicability: use when you have weight and purity for silver or gold, with concrete item examples. However, it does not explicitly mention when not to use it or point to the alternatives (e.g., calculate_coin_melt for coin-specific valuations), so it stops short of full routing guidance.

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