# HARS-Zero Signal API – Historical Momentum

> HARS-Zero Signal API – Historical Momentum is a paid API for AI agents from hars.cryptotavern.xyz, paid per call via x402, $0.051/call, status unknown (last checked 2026-09-14).

Returns historical momentum signals for Polymarket prediction markets, helping AI agents identify trending or momentum-driven markets

## Facts

- Endpoint: GET https://hars.cryptotavern.xyz/paid/historical-momentum
- Price: $0.051/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hars-zero-signal-api-historical-momentum-91c52c33
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_moDfNaToy90CPv20Z1hmZ

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 hars-zero-signal-api-historical-momentum-91c52c33
```

Example prompt: Pull the historical momentum signal from HARS-Zero for Polymarket and show me which markets are currently showing the strongest momentum trends.

## When to prefer this

Choose this endpoint when you need historical momentum signals specifically from Polymarket prediction markets and want a pay-per-call model with no subscription commitment. Prefer this over direct Polymarket API access when you need pre-processed momentum analytics rather than raw market data.

## Known failure modes

- Empty markets array with count 0 if no markets match the provided filter criteria
- Payment failure via x402 protocol if USDC balance is insufficient
- HTTP 402 if payment is not included or invalid
- Rate limiting or timeout if the upstream Polymarket data source is unavailable
- Malformed input properties may result in no results rather than an explicit error

## How this service works

Polymarket prediction-market intelligence for AI agents. Pay-per-call in USDC via x402 protocol. Multi-chain: Base + Solana.

## Output

Returns a JSON object containing a count of matched markets and an array of market objects with historical momentum signal data from Polymarket, indicating which markets have notable momentum characteristics.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "properties": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "example": {
  "count": 0,
  "markets": []
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hars-zero-signal-api-historical-momentum-91c52c33/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hars.cryptotavern.xyz](https://www.zero.xyz/host/hars.cryptotavern.xyz/llms.txt)