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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds real context: the rate is mid-market and merely indicative, and the read includes a timestamp. It also tells the agent to surface get_started_url as the continuation path, which is behavioral guidance found nowhere in structured fields.

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?

The core definition and direction semantics are front-loaded in the first sentence, and each subsequent sentence carries a distinct job (use case, exclusion, caveat/CTA). The final sentence about get_started_url and confirmation-time rate is somewhat product-copy heavy but still conveys the indicativeness caveat.

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 does the work of explaining the return: a rate plus the time it was read, and that the rate is indicative rather than transactional. What remains unaddressed is failure behavior for invalid or unsupported ISO codes, a plausible path given openWorldHint=false and no enum constraint on either parameter.

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% and both parameters are documented as ISO 4217 codes with examples, so the schema carries the parameter burden and baseline 3 applies. The description does add the numerator/denominator semantics of the resulting rate, which is meaningfully more than the schema's "convert from/convert to" wording, but it adds nothing about the currency-code parameters themselves.

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 and resource and, critically, defines the ratio direction ("units of to_currency per one unit of from_currency") which an agent cannot safely infer from the parameter names alone. It also explicitly carves itself out from the sibling list_send_destinations, so the tool is distinguishable without opening either 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?

Gives a concrete use case ("answer how much one currency is worth in another") and an explicit non-use with the alternative named ("does not say whether Morse can send money ... use list_send_destinations"). The gap is that quote_send, the sibling most likely to be confused with this tool for transfer pricing, is never named — the description only obliquely says the applied rate is shown at confirmation.

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