Central bank policy rates for 39 economies from BIS official data: current rate, date of last change and size in bp, year-ago rate, central bank name. Filter by ISO country codes (US, XM for euro area, MA, ZA...). Price: $0.003 USDC per call, paid with x402 on Base.
| Name | Required | Description | Default |
|---|---|---|---|
| country | No | Comma-separated ISO2 codes; XM = euro area. Omit for all 39. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden, and it does disclose the important non-obvious traits: the data source (BIS official), the exact coverage count, and crucially a per-call price of $0.003 USDC paid via x402 on Base, which tells the agent this call has a real monetary cost and a payment prerequisite. It does not state freshness/latency beyond the year-ago field or describe error/rate-limit behavior, keeping it short of 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?
Three short sentences, front-loaded with what the data is, followed by filtering then cost. Every sentence adds something distinct and nothing is repeated.
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?
There is no output schema, so the description must describe returns, and it does so explicitly (current rate, date of last change and size in bp, year-ago rate, central bank name) along with data source and scope. An agent has everything needed to decide and call correctly.
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%, so the parameter is already fully documented. The description's 'US, XM for euro area, MA, ZA' examples mostly restate the schema's 'XM = euro area' note, adding marginal value only as concrete example codes; baseline 3 is appropriate.
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?
A specific verb+resource statement: it names the exact dataset (BIS central bank policy rates), the coverage (39 economies), and enumerates fields returned. This is clearly distinguishable from sibling macro_fx, which covers exchange rates rather than policy rates, without needing to name it 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?
Usage is implied by the domain and the filter instructions ('Filter by ISO country codes... Omit for all 39'), but there is no explicit when-to-use/when-not or routing note versus siblings like macro_fx. An agent can infer usage from the resource itself, which is the minimum-viable level.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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