Payment rails of a country today

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

With no annotations, the description carries the full burden and does well: it discloses the status enum (healthy/degraded/outage/no_data), that a start time and citation accompany each status, what the health index means (100 = the rail's own norm), and that free-tier data is one day behind and currency-limited. It doesn't mention rate limits or auth mechanics beyond the existence of Pro keys, which keeps it from a 5.

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?

Content is front-loaded: what it returns, the status model, then tier access. The long parenthetical method-class list is information-dense rather than filler, though the tier sentences drift toward promotional framing and could be tightened.

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 shape needn't be restated, yet the description usefully previews the key fields anyway; it also compensates for missing annotations by covering status semantics and data freshness. An agent has enough to call it correctly, with only auth/rate-limit mechanics left implicit.

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?

There is a single parameter with 100% schema description coverage (ISO 4217 code with examples), so the schema already does the explanatory work. The description adds only the framing that the query is per-country/per-currency and date-sensitive, which is marginal but consistent with the baseline.

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 names a concrete resource (per-currency payment rail health) and enumerates its dimensions: method class, direction, status vocabulary. That scope cleanly separates it from siblings like get_rail_incidents or get_stress_signals, though those siblings are never named. It reads more as a capability pitch than a crisp 'returns X for Y' statement, costing it the top score.

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 implied by the content (look up rail reliability for a currency), and the free-vs-Pro tier split tells the agent what data depth is available. However, there is no explicit when-to-use/when-not guidance and no alternative tool is named for adjacent questions (incidents, stress signals, street rates).

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