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

With readOnlyHint, idempotentHint and destructiveHint already in annotations, the description earns credit for disclosing genuinely non-obvious behavior: per-metal feeds can fail independently and the error is returned inline rather than failing the whole call. That partial-failure semantics is not derivable from any structured field. It omits price freshness/timestamp behavior, so not 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: the first front-loads what is returned and in what units, the second carries the one caveat worth knowing. Nothing repeats the schema or annotations.

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 single optional parameter and no output schema, the description covers the metals, the units, the currency dimension and the failure mode. It leaves open whether prices are real-time vs delayed and what timestamp accompanies them, which matters for a 'live spot' tool.

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 the currency parameter already documents the ISO 4217 format, default and examples. The description adds only 'any major currency', which slightly broadens but does not deepen the schema's meaning. Baseline 3 is appropriate.

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?

States a specific verb+resource: live spot prices for four named metals (with tickers) in three weight units and any major currency. It is clear what the tool returns, though it never explicitly contrasts itself with the gold-only sibling get_gold_price_per_gram.

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 is implied rather than stated: the multi-metal, multi-unit framing suggests using this instead of the per-gram single-metal sibling, but no alternative is named and no when-not condition is given. An agent must infer the routing from the field list.

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