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

With no annotations, the description carries the full burden. It does disclose a meaningful behavioral constraint (results are limited to what a paid plan carries) and that both FX pairs and spot metals are returned, but says nothing about result size, pagination, or whether listing requires auth.

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, front-loaded sentence with no filler. The phrasing 'a paid plan carries' is slightly indirect but conveys the scope efficiently.

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 is present, so return-value detail is not required. For a zero-parameter read-only list tool, the description covers resource, scope, and fields adequately; only eligibility/authentication details are left implicit.

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?

The tool takes zero parameters, so the baseline of 4 applies. There is no parameter behavior for the description to clarify or obscure.

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 names a specific resource (FX pairs and spot metals) and scopes it to what a paid plan carries, along with the returned attributes (name, class). It is clearly distinguishable from candle/quote/offer siblings, though it never explicitly names them.

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: the agent must infer this is the discovery step for finding tradable symbols. The 'paid plan' mention hints at an eligibility prerequisite, but there is no explicit when-to-use or when-not-to-use guidance relative to get_offer or quote_price_for.

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