JPY exchange rates and conversions.
Scored across 3 tools
The three tools have mostly distinct purposes: convert returns a converted amount, fx_rate returns a single-currency rate, and fx_table returns multiple rates. There is minor overlap between convert and fx_rate because both involve JPY vs one other currency, but the output type distinguishes them.
All names use snake_case, but conventions are mixed: convert is a verb while fx_rate and fx_table are noun phrases. The pattern is readable but not fully predictable.
Three tools are well-scoped for a narrow JPY FX rates server: one for conversion, one for single-currency rates, and one for a rate table. Each earns its place without redundancy.
The core spot-rate and conversion workflows are covered. Minor gaps remain, such as historical rates or time-series data, but agents can handle typical JPY exchange-rate tasks with this surface.
PRO. Convert an amount between JPY and another currency.
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | ||
| from | Yes | ||
| amount | Yes | ||
| access_token | No | Subscriber token from /success (or Authorization: Bearer) |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
There are no annotations, so the description carries the entire behavioral burden, and it discloses almost nothing: it doesn't say whether the rate is live or cached, is silent on the subscription/access_token requirement that the schema hints at, and says nothing about reversibility or response shape. Only the "PRO." marker hints at a paid tier.
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 short sentences, front-loaded with the action and the scoping constraint. Nothing is redundant or padded.
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 four parameters, 25% schema coverage, no annotations and no output schema, the description should say more than it does – the auth path, the direction of conversion, and what the tool returns (converted amount, rate used) are all absent. An agent can guess the call shape but not the contract.
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 only 25% – `from` and `to` have no descriptions at all – so the description must compensate. It does add the meaningful constraint that one of the two currencies must be JPY, but it leaves ambiguous whether `from` or `to` must be the yen side, gives no currency-code format, and doesn't say whether `access_token` is mandatory.
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?
"Convert an amount between JPY and another currency" states a specific verb (convert) and resource (monetary amount) plus a scope constraint (one leg must be JPY). It is clear on its own, but it never names or distinguishes itself from the siblings fx_rate and fx_table, so an agent can't route between the three from this text alone.
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 only implied: the JPY constraint tells the agent the tool applies to yen pairs, but there is no statement of when to prefer it over fx_rate (single rate lookup) or fx_table (bulk rates). No explicit when-not cases and no named alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
FREE. Latest JPY exchange rate vs one currency (e.g. USD, EUR, GBP, AUD).
| Name | Required | Description | Default |
|---|---|---|---|
| currency | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must carry the full behavioral burden. It usefully discloses that the tool is FREE and returns the latest rate, but it does not explain rate source, freshness guarantees, auth requirements, rate limits, or return format.
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 description is a single compact sentence with no wasted text, and the key scope information is front-loaded. 'FREE' is brief and useful for cost-sensitive selection.
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 simple one-parameter rate lookup, the description gives enough to identify the base currency and target currency examples. However, with no annotations and no output schema, it should say more about the return value shape or source/freshness to be fully self-contained.
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?
The schema has one required parameter with 0% description coverage, so the description adds important meaning by indicating that 'currency' is the quote currency against JPY and by giving examples such as USD, EUR, GBP, and AUD. It still does not specify exact ISO code formatting or case sensitivity, but it substantially compensates for the schema gap.
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 clearly states the resource and scope: the latest JPY exchange rate against a single currency, with examples. It is specific enough to distinguish the basic operation, but it does not explicitly differentiate itself from sibling tools such as convert or fx_table.
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 phrase 'vs one currency' implies this tool is for retrieving a single latest rate, which hints at when to use it instead of a table or conversion tool. However, it does not name alternatives or state when not to use it, so the guidance remains implicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
PRO. Latest JPY rates vs USD,EUR,GBP,AUD,CAD,CHF,CNY,KRW.
| Name | Required | Description | Default |
|---|---|---|---|
| access_token | No | Subscriber token from /success (or Authorization: Bearer) |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It mentions “PRO” and “Latest” but does not state auth requirements clearly (access_token is optional in the schema), rate limits, refresh cadence, or whether the operation is strictly read-only.
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 description is two short fragments with no wasted words. “PRO” and the currency scope are front-loaded and directly relevant to the tool's purpose.
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 simple one-parameter read tool this is minimally adequate: it identifies the data and currency set, and the parameter is fully covered by the schema. However, with no annotations and no output schema, it should do more to explain authentication and what the returned rates table looks like.
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 the single optional access_token parameter is already fully documented in the schema. The description adds no parameter-level semantics beyond what is structured, so the baseline of 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?
States the specific resource (latest JPY rates) and enumerates the currencies covered, so an agent can tell what data is returned. It does not explicitly clarify how this differs from the sibling fx_rate or convert tools, but the plural/table framing is reasonably distinct.
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?
Provides no guidance on when to use fx_table instead of fx_rate or convert. The only usage-related signal is “PRO,” which hints at subscription gating but does not explain selection criteria or alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
convertfx_ratefx_tableWhich JPY rate did Japan Customs publish for a date? Is a firm on an FSA list? Hosted. No advice.
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