# Base Token Holder Sketch API

> Base Token Holder Sketch API is a paid API for AI agents from xx402.icu, paid per call via x402, $0.01/call, status down (last checked 2026-09-15).

Returns a sketch of observed token holders, whale candidates, contract holders, and recent transfer activity for a Base ERC20 token within a specified block window, including risk flags.

## Facts

- Endpoint: GET https://xx402.icu/x402/api/base-token-holder-sketch
- Price: $0.01/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-token-holder-sketch-api-7cf9665b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_hMnJ_HdooeSuP3VsQg5gf

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 base-token-holder-sketch-api-7cf9665b
```

Example prompt: Can you pull a holder sketch for the Base token at 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 — look at the last 500 blocks and return up to 15 top observed holders, whale candidates, and any risk flags around concentration?

## When to prefer this

Use this endpoint when you need a quick, low-cost ($0.01 USDC) onchain snapshot of who holds a Base ERC20 token, especially to detect whale concentration, contract-controlled supply, or suspicious holder patterns. Prefer this over full indexer queries when you need fast, actionable holder risk signals rather than exhaustive historical data.

## Known failure modes

- Invalid token_address format (not a valid 0x ERC20 address) returns 400 error
- window_blocks below minimum of 100 or above maximum of 1000 returns validation error
- Token with no transfer activity in the specified block window returns empty holder sets
- Payment not provided or insufficient USDC results in 402 Payment Required
- Token contract does not exist on Base returns empty or error response
- limit parameter out of range (below 1 or above 20) returns validation error

## How this service works

Paid x402 buyer market scout, x402 paid resource preflight, x402 seller visibility audit, Base actionable risk feed, liquidity exit risk alerts, pool launch risk feed, stable asset risk feed, contract control event feed, protocol outflow risk feed, yield pool allocation risk feed, protocol fee quality feed, token watchlist decision packet, wallet watchlist decision packet, approval risk feed, ranked DeFi review queues with incident history, onchain risk decision packet, promoted token campaign decision packet, large transfer decision packet, token candidate screening decision radar, DEX pair anomaly decision radar, wallet safety decision packet, counterparty flow, allowance, approval exposure, DEX pair routing risk, token trade safety, token liquidity, token flow, holder concentration, contract controls, batch token screening decision packets, token diligence, and BTC15 prediction-market microstructure, execution-friction, calibration-slice, recent market tape, resolved feature sample, and threshold-pressure packets for agents and risk tools.

## Output

Returns a JSON object with a summary of holder activity, top observed holder candidates, active whale candidates, contract holder candidates, a sample of recent transfers, risk flags indicating concentration or anomaly concerns, and data sources — all derived from onchain Base block activity within the specified window.

## Response schema (JSON Schema)

```json
{
 "keys": [
  "summary",
  "holder_concentration_decision",
  "priority_queue",
  "best_next_products",
  "concentration_breakdown",
  "review_queue",
  "avoid_queue",
  "top_observed_holders",
  "active_whale_candidates",
  "contract_holder_candidates",
  "recent_transfer_sample",
  "bucket_counts",
  "risk_flags",
  "risk",
  "source_status",
  "sources"
 ],
 "type": "json"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-token-holder-sketch-api-7cf9665b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from xx402.icu](https://www.zero.xyz/host/xx402.icu/llms.txt)