# Base Token Sell Check at Your Size

> Base Token Sell Check at Your Size is a paid API for AI agents from base-facts.yankii.fr, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-13).

Simulates a buy and immediate sell of a Base token at a specified ETH trade size to report buy tax, sell tax, and round-trip loss including price impact — without sending a real transaction.

## Facts

- Endpoint: POST https://base-facts.yankii.fr/v1/sellcheck/size?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-token-sell-check-at-your-size-ccba8d50
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0qOqUMgkb_6bO4dzpv4_V

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-sell-check-at-your-size-ccba8d50 -d '<json body>'
```

Example prompt: Before I trade, can you simulate buying and then immediately selling 0.5 ETH worth of token 0x4200000000000000000000000000000000000006 on Base and tell me the buy tax, sell tax, and total round-trip loss including price impact?

## When to prefer this

Use this endpoint instead of the basic sell check when you need to measure tax and price impact at a specific trade size (0.001 to 10 ETH), not just at a minimal dust amount. This is especially valuable for larger trades where price impact is significant, or when you want realistic honeypot detection at your actual intended trade size rather than an optimistic small-size estimate.

## Known failure modes

- Token address is invalid or not a contract — returns error or zero results
- Trade size outside 0.001–10 ETH range — returns validation error
- Token has no liquidity on supported DEXes — unable to simulate trade
- eth_call fails due to RPC timeout or Base node unavailability
- Token contract is malformed and reverts during simulation

## How this service works

Base token sell check AT YOUR TRADE SIZE: simulates a buy of amountEth (0.001 to 10 ETH) and an immediate sell inside eth_call (no trade is sent) and reports the buy tax, the sell tax and the round-trip loss including price impact. Uniswap v2, v3, v4 (ETH, WETH, ZORA, USDC quotes) and Aerodrome. Measured at one block, not a guarantee, not financial advice.

## Output

Returns the buy tax percentage, sell tax percentage, and round-trip loss (including price impact) for the simulated trade, sourced from Uniswap v2/v3/v4 and Aerodrome DEX quotes on Base, all computed via eth_call without any on-chain transaction.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "token": {
   "type": "string",
   "description": "Token contract address (0x-prefixed hex, 20 bytes)"
  },
  "amountEth": {
   "type": "string",
   "description": "Trade size in ETH as a decimal string, from 0.001 to 10 (example: \"0.5\")"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-token-sell-check-at-your-size-ccba8d50/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-facts.yankii.fr](https://www.zero.xyz/host/base-facts.yankii.fr/llms.txt)