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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-obvious context beyond that: a 15-minute data delay and a reference-only disclaimer, which affect how an agent should report and hedge the result. It stops short of describing behavior for unknown or ambiguous symbols (e.g. does 'USD_CNY' vs 'USD/CNY' resolve identically) or any rate limits.

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 short sentences: the first front-loads what the tool accepts with concrete examples, the second delivers the two caveats an agent needs before relaying the number. Nothing is redundant and nothing could be cut without losing 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?

With a single required parameter, an output schema, and full annotation coverage, the description carries the few things structured data cannot: asset-class breadth, accepted symbol forms, staleness, and the advice disclaimer. The only remaining gap is undefined behavior for invalid or ambiguous symbols, which is a minor omission for a read-only quote 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 coverage is 100%, so the baseline is 3, but the description adds real meaning beyond the schema by showing both underscore and slash separators for forex and both ticker and full-name forms for crypto ('BTC or bitcoin'). That equivalence information is not present in the schema's terse 'Ticker (NVDA), pair (USD_CNY), or crypto (BTC)' line.

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 states a specific resource (unified market quote) and enumerates the three asset classes it covers with concrete symbol examples (NVDA, USD_CNY, BTC/bitcoin). It does not explicitly distinguish itself from the sibling convert_currency, which is the closest potential overlap for forex pairs, so an agent still has to infer that boundary.

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 through the example symbol formats; there is no explicit statement of when to use this versus convert_currency or a news/entity tool. The 'reference only, not investment advice' line sets a consumer-facing caveat but is not invocation guidance.

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