# CoinCap Market Cap History

> CoinCap Market Cap History is a paid API for AI agents from rest.coincap.io, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).

Returns historical market capitalization data for a specific cryptocurrency asset by slug

## Facts

- Endpoint: GET https://rest.coincap.io/v3/agentFriendly/asset_mcap_history/%7Bslug%7D
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/coincap-market-cap-history-35ca7a71
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_7jPdRL_uUyiZhpBUfh523

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 coincap-market-cap-history-35ca7a71
```

Example prompt: Can you pull the historical market cap data for bitcoin from CoinCap so I can see how its market capitalization has changed over time?

## When to prefer this

Use this endpoint when you need historical market capitalization data for a specific cryptocurrency identified by its CoinCap slug. Prefer this over price history endpoints when the analysis specifically concerns market cap (circulating supply × price) rather than raw price. It is ideal for trend analysis, valuation context, or comparing a coin's growth trajectory over time. The x402 per-call payment model makes it accessible without API key registration for one-off agent queries.

## Known failure modes

- Invalid or misspelled asset slug returns a 404 or empty dataset
- Unknown slug not in CoinCap database returns an error
- Missing or invalid API key / failed x402 payment returns 401 or 402
- Rate limiting may occur if too many requests are made in quick succession
- Network timeouts for slow connections

## How this service works

CoinCap gives AI agents, apps, and developers real-time cryptocurrency market data.

Two ways to access:
- **API key** — sign up at https://coincap.io and pass `Authorization: Bearer <key>` or `?apiKey=<key>`.
- **Keyless x402** (agents) — the 10 `agentFriendly` endpoints accept per-call USDC payment on Base via the [x402 protocol](https://x402.gitbook.io/x402). No signup needed. See `/.well-known/x402.json` for the machine-readable payment catalog.

## Output

Returns a time-series dataset of market capitalization values for the specified cryptocurrency, including historical data points with timestamps and corresponding market cap figures in USD, allowing trend analysis over time.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "slug"
 ],
 "properties": {
  "slug": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/coincap-market-cap-history-35ca7a71/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from rest.coincap.io](https://www.zero.xyz/host/rest.coincap.io/llms.txt)