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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world hint, so the safety profile is covered. The description adds context annotations do not carry — that the call is free and requires no API key, removing a common hesitation about making a preparatory lookup. It does not describe the shape of the returned list, but this is a trivial zero-arg enumeration.

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 short sentences, each doing distinct work: what it returns, when to call it, and cost/auth. The scoping statement comes first, so the agent gets the core fact immediately.

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 zero-argument lookup with no output schema, the description conveys the content of the result well enough to decide and call. Only minor gap is whether results are grouped by asset class or returned as a flat list, which the phrase 'every crypto, metal and currency symbol' only loosely implies.

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 no parameters and the schema is an empty object at 100% coverage, so there is nothing the description must compensate for. Baseline 4 applies; no parameter detail is missing or needed.

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 (the set of symbols get_price supports) and bounds it to crypto, metal and currency. An agent can instantly distinguish it from get_price and from unrelated siblings like get_token_price or list_models.

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?

Explicitly says to call it before get_price when unsure a symbol is covered, which names both the trigger condition and the alternative tool. The implicit inverse (skip it when you already know the symbol) is clear from that framing.

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