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

Annotations already cover read-only/idempotent/open-world safety, and the description adds genuinely non-structured context: the rate comes from a static table (staleness implication), the result includes the inverse, and it carries a signed receipt. It does not explain what the receipt is for or how it should be verified, leaving one behavioral gap.

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 sentences, zero filler, and the most decision-relevant fact (static, not live) is front-loaded before the return-shape details.

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 two-parameter read tool with a full output schema and safety annotations, the description covers what it does, how it differs from live feeds, and what it returns. The only omission is the meaning/use of the 'signed receipt' (e.g. whether receipt_verify should be used), which leaves a minor loose end.

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% with both required params (base, quote) documented and exemplified, so the schema already carries the parameter meaning. The description only implies base/quote via 'fiat and stablecoin conversion rate' and adds no syntax or constraint detail beyond the schema, so 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+resource ('reference fiat and stablecoin conversion rate') and distinguishes itself from live-quote siblings (check_price, crypto_ticker) by explicitly saying 'from a static table, not a live feed'. It does not name a sibling directly, but the static-vs-live framing is enough for an agent to route correctly.

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?

The 'static table, not a live feed' clause functions as an explicit when-to-use/when-not discriminator against the live-price siblings, which is real routing guidance. It stops short of naming alternatives or stating prerequisites (e.g. supported symbol set, staleness expectations), so it isn't a full 5.

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