Hourly street rates (Pro)

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

With no annotations, the description carries the full burden and does disclose two real behavioral facts: the tier restriction (Pro/Enterprise keys) and the data latency ('hours arrive with the daily update'). It stops short of saying how a non-Pro key fails or whether partial-day data is returned before the update, but the auth and freshness disclosure is above average for an unannotated tool.

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 dense sentence that front-loads what is returned before naming the summary fields and access constraints. No wasted words, though the parenthetical field list slightly compresses readability.

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 exists so return values need not be explained, and the two parameters are fully documented. Combined with the tier and update-timing notes, the agent has enough to call it correctly; only the failure mode for non-Pro keys is left unstated.

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% and both parameters are documented there (ISO 4217 code, YYYY-MM-DD with today default). The description reinforces the date semantics ('per UTC hour for one day') but adds no syntax or format 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 ('The street rate of a currency per UTC hour for one day') and enumerates the included summary fields. The hourly granularity implicitly distinguishes it from get_street_rate and get_rate_history, but it never names those siblings explicitly.

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 description gives a usage condition ('Pro and Enterprise keys; hours arrive with the daily update') that tells an agent about eligibility and data freshness. It does not say when to prefer this over get_street_rate or get_rate_history, so the agent must infer the choice from the granularity wording alone.

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