Indicative USDC → local-currency rate at our sale price, with an estimate for an amount. The quote is the binding price.
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | ISO-4217, e.g. INR | |
| type | No | what the rate is for; default payout | |
| amount | No | an amount in the local currency `to`, to estimate its USDC price, e.g. 5000 |
Changes observed during successful MCP inspections.
Input schema / properties / amount / descriptionAdded value: +"an amount in the local currency `to`, to estimate its USDC price, e.g. 5000"Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare a safe, idempotent read, so the description's job is adding semantics — and it does: the rate is indicative rather than binding, it is 'our sale price' (i.e., includes spread, not a mid-market rate), and the amount form is only an estimate. Missing is any statement about rate freshness or caching, which matters for a pricing read.
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 with the core operation front-loaded and no filler. The second sentence is slightly compressed — 'The quote' relies on the reader mapping it to the sibling tool rather than the returned object — but it earns its place as the disambiguator.
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 is the only place to learn what comes back, and it only vaguely says 'rate ... with an estimate for an amount' — no indication of rate precision, which currency the estimate is expressed in, or error behavior for unsupported codes. Adequate to call, not quite adequate to interpret the result confidently.
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%, so `to`, `type`, and `amount` are all documented in structured fields; the description only restates that an amount produces an estimate. It adds no insight on how `type` (topup/bill/payout) changes the rate, which is the least obvious parameter.
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?
Names a specific resource and direction (USDC → local-currency rate) plus the pricing basis (sale price) and the optional estimate behavior. The closing sentence implicitly contrasts it with the `quote` sibling by declaring which price is binding, so an agent can tell the two apart, though the terse name `fx` carries none of this on its own.
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 quote is the binding price' implies the split: use this for indicative/preview pricing and `quote` when the price must bind. That is a real routing signal, but it is stated indirectly and never says explicitly when not to rely on this tool (e.g., don't use the returned rate to finalize a transaction).
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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