# rate-hub API MCP Endpoint

> rate-hub API MCP Endpoint is a paid API for AI agents from x402-v1.sky-1.org, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-11).

Provides access to rate-hub API capabilities via MCP (Model Context Protocol) JSON-RPC 2.0 interface, gated by x402 USDC micropayment on Base

## Facts

- Endpoint: POST https://x402-v1.sky-1.org/mcp?utm_source=zero.xyz
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/rate-hub-api-mcp-endpoint-41fdc0d7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_WcBRAfR7zYyJo5R4BfYg6

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability rate-hub-api-mcp-endpoint-41fdc0d7 -d '<json body>'
```

Example prompt: Can you query the rate-hub API for current rate data using the MCP interface? I'll pay with USDC on Base — use my credit token if I have one, or initiate a new x402 payment to get a pack of requests.

## When to prefer this

Choose this endpoint when you need to interact with rate-hub API capabilities through the standardized Model Context Protocol (MCP) JSON-RPC 2.0 interface and are operating in an x402-enabled environment that can handle USDC micropayments on Base. Prefer this over direct REST endpoints when your agent framework natively supports MCP tool discovery and invocation.

## Known failure modes

- 402 response if no valid credit token and no payment signature provided
- 402 if credit token is spent or expired — must re-pay
- 402 if payment cannot be accepted (invalid signature, wrong amount, wrong scheme)
- MCP-wrapped 200 with error body if JSON-RPC method is unknown or params are malformed
- Network timeout if Base blockchain payment verification is slow

## How this service works

**Access.** A deployment runs in one of two modes and the free `GET /v1/x402` tells which: it answers `200` with the offer on an x402 deployment and `404` on a classic one.

- **x402 deployment** (the public one). There is no API key. A payment of USDC on Base buys a credit token for a pack of requests. Call a paid route without credentials: the answer is `402` with the offer in the `PAYMENT-REQUIRED` header (base64 JSON) and in the body. Pay by repeating the request with a `PAYMENT-SIGNATURE` header (base64 JSON x402 v2 `PaymentPayload`, scheme `exact`). The paying response is the normal answer plus `X-Credit-Token` (your token), `X-Credit-Remaining` and `PAYMENT-RESPONSE`. Keep the token and send `Authorization: Bearer <token>` on every later request. A token that is unknown, spent or expired, and any payment that cannot be accepted, answer `402` again: every payment problem is a `402` with a snake_case reason in `error`, never a `400`. On `/mcp` the same problems come back as `200` tool results, see `/mcp`. A `503` with `Retry-After` can mean the same payment is being processed right now: retry shortly. If the payment facilitator does not answer, the answer is `502` and nothing is charged.
- **Classic deployment.** The client sends its key in the `X-API-Key` header. A missing or unknown key answers `401`.

Paid routes: every `/v1` path except `GET /v1/x402`, and MCP `tools/call`. Free: `GET /v1/x402`, `/healthz`, `/readyz`, `/version`, `/openapi.yaml`, `/openapi.json` and `/.well-known/x402` (x402 deployments only), `/docs` (with `/docs/behavior` and `/docs/behavior.md`), `/llms.txt`, and the MCP methods `initialize`, `ping`, `tools/list` and `notifications/*`. On an x402 deployment every served request costs one credit, whatever its status, except `5xx`, which is refunded. Requests that match no route (`404`, `405`) are free.

Client rules, in order. Read these before the paths.

- Ignore unknown JSON fields. The server adds fields without a new major version.
- Map an unknown enum value to an `unknown` case. A Swift `Codable` enum with no fallback crashes the decode and drops the whole response.
- Honor `Retry-After` on `429` and `503`. The header is always an integer number of seconds, never an HTTP-date. `pending` rates carry `retry_after` in seconds for that asset only.
- Fiat live quotes: `source_code` `s10` is a live rate table with no observation time of its own, so `as_of` is the fetch instant (about every 30 minutes by default); `day_change_pct` and `high_volatility` stay a move against the last rate of the previous UTC day, not against the previous poll. A currency that table does not cover keeps its last quote (`source_code` `s3`, `as_of` midnight UTC of that document's date) and turns `stale` after the fiat stale limit. Fiat daily quotes (`/v1/rates/daily`, `source_code` `s3`): `as_of` is midnight UTC of the upstream document date (the rate for that UTC calendar day), not the fetch instant. When present, optional `day` (`YYYY-MM-DD`) repeats that calendar day explicitly. Optional `fetched_at` is when rate-hub last received the live quote from upstream.
- Freshness: live responses (`/v1/rates`, `/v1/top`, `/v1/assets`, `/v1/meta`, errors) carry `Cache-Control: no-cache`, so a client or CDN must ask again before reusing one. A refresh always returns the newest snapshot rate-api holds, so the collector's polling cadence is the floor on freshness. Judge a price by `as_of` (when the price was observed) and `fetched_at` (when rate-hub last refreshed it), not by when you asked.
- `server_time`, quote `as_of`, and quote `fetched_at` use RFC3339 with millisecond precision (fractional seconds trimmed; no sub-millisecond noise).
- Integration tests can observe `pending` by requesting a catalog uid that has no row in the loaded in-memory quote snapshot (for example a cold asset before the first lazy fetch).
- Back off exponentially with jitter. Do not retry in a tight loop.
- Prices and percent changes are decimal strings, never JSON numbers. Parse them with a decimal type. Do not use binary floating point.

Edge cases this schema does not show (dynamic coins and their changing uids, placeholder icons, series limits, data lifetimes) are in the [behaviour notes](/docs/behavior) ([raw Markdown](/docs/behavior.md)).

Conventions: lowercase `snake_case`, full field names, statuses as strings, versioned under `/v1`. Changes inside v1 are additive only.

Prices are rounded to 10 significant digits. This service is an indicative cache, not an oracle. Live `/v1/rates` quotes are not a full history product; additive `/v1/rates/daily` returns one immutable USD (or requested `vs`) rate per catalog uid per UTC calendar day for backfill and prewarm (see those paths for day definitions and archive limits).

## Output

A JSON-RPC 2.0 response object containing the result of the requested MCP method call, along with HTTP headers including X-Credit-Token, X-Credit-Remaining, and PAYMENT-RESPONSE when a payment was processed. Errors are returned as 200 responses with JSON-RPC error payloads following MCP conventions.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "method",
  "jsonrpc"
 ],
 "properties": {
  "id": {
   "type": "string",
   "description": "Request id, a string or an integer. Absent for a notification."
  },
  "method": {
   "type": "string"
  },
  "params": {
   "type": "object"
  },
  "jsonrpc": {
   "enum": [
    "2.0"
   ],
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "description": "JSON-RPC 2.0 response."
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/rate-hub-api-mcp-endpoint-41fdc0d7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-v1.sky-1.org](https://www.zero.xyz/host/x402-v1.sky-1.org/llms.txt)