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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description goes further by naming the upstream data sources (gold-api.com and open.er-api.com), noting the returned timestamp, and flagging the world-market indication caveat — genuine context beyond the annotations, though caching/freshness or rate-limit behavior is unstated.

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, front-loaded with the core deliverable and units before the data-source provenance and caveat. Dense but each sentence contributes; the source attribution is arguably secondary and could be trimmed.

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 must convey the return shape, and it does: price per gram, troy ounce and kilogram plus the read timestamp, in the requested currency. Combined with the market-indication caveat, an agent has everything needed to call and interpret it.

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 both parameters are already documented with their ISO 4217 pattern and default. The description restates the currency examples and format but adds nothing new, and it never mentions the 'lang' parameter at all. Baseline 3 applies when the schema carries the parameter burden.

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 resource (today's world spot gold price) with explicit units (one gram, one troy ounce, one kilogram of fine gold) and scope (the currency asked for). The closing line 'A world-market indication, not what any dealer pays or charges' implicitly separates it from the sibling gold_buyback_prices, so an agent can distinguish it without opening the 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 is implied rather than stated: the market-vs-dealer caveat steers the agent away from buyback tools, but there is no explicit 'use X instead' or condition listing. No prerequisites or exclusions (e.g. historical prices, date arguments) are given.

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