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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds only the temporality detail (current plus previous session) and currency/unit flexibility; it says nothing about freshness guarantees, network dependency despite openWorld, or failure modes.

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?

A single well-formed sentence, front-loaded with what is returned, with no filler or redundancy. Every clause carries information.

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?

An output schema exists to cover the return shape and annotations cover the safety profile, so the description only needs to frame scope — which it does. It stops just short of explicitly routing the agent away from the neighboring history and Goldback tools.

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%, so base, unit and metals are fully documented in the schema, including defaults and the Goldback exclusion. The description restates the currency and unit concepts but adds no syntax or constraint detail 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?

States a specific verb (retrieves spot prices) and resource, and enumerates the covered metals, currency and unit options. The 'current and previous-session' framing implicitly separates it from get_price_history, but it never names that sibling, so the differentiation is left to inference.

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 only implied: 'current and previous-session' suggests this is for latest pricing rather than a time series, but there is no explicit when-to-use, when-not-to-use, or pointer to get_price_history / get_goldback_rate as alternatives. An agent must infer the routing.

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