---
title: "Get Arkham Altcoin Index"
method: POST
path: "/marketdata/altcoin-index"
tags: ["Marketdata"]
---

# Get Arkham Altcoin Index

`POST /marketdata/altcoin-index`

## Request

- Base URL: `https://api.arkm.com/x402`
- URL: `https://api.arkm.com/x402/marketdata/altcoin-index`
- Auth: none required

Get Arkham Altcoin Index. $0.20 per call.

## Request body

- object

## Response `200`

Successful response

- unknown

## Other responses

- `400`: Fatal for the request as written: validation failed or required JSON body fields are missing. Fix the request; do not retry it unchanged. Payment is not settled.
- `402`: Payment challenge, not an application error. Read the base64 x402 v2 challenge from PAYMENT-REQUIRED, sign it, and retry the same request with PAYMENT-SIGNATURE. If a post-payment 402 omits PAYMENT-REQUIRED, verification failed: read the new challenge, re-sign, and retry once.
- `404`: The upstream Arkham resource does not exist. Fatal for the same input. Payment is not settled.
- `429`: Per-wallet endpoint rate limit exceeded. Retry with at least 1 second of backoff; keep heavy endpoints at no more than 5 requests per second.
- `5XX`: Arkham failed or timed out, including 502 and 504 responses. Retry with backoff. x402 payments and MPP transaction credentials are not settled for failed requests; MPP hash credits are redeemed at admission and are not refunded automatically.

## Changes

- **2026-10-27** `60e4a5fdbecc`: 1 breaking
  - request property `additionalProperties/anyOf[subschema #4]/items/` list-of-types was narrowed by removing types `boolean and number` from media type `application/json`

[Operation history](https://skmtc.dev/arkm/apis/arkham-x402/changes/marketdata/altcoin-index/post.md)

---

[API](https://skmtc.dev/arkm/apis/arkham-x402.md) - [All operations](https://skmtc.dev/arkm/apis/arkham-x402/llms.txt) - [OpenAPI document](https://skmtc.dev/arkm/apis/arkham-x402/revisions/60e4a5fdbecc?raw)