# Base Toolbox Uniswap v3 Preflight Check

> Base Toolbox Uniswap v3 Preflight Check is a paid API for AI agents from basetoolbox.cartonpliant.workers.dev, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-15).

Validates a Uniswap v3 swap on Base before signing — checks token sellability, expected output amount, and warnings about the transaction.

## Facts

- Endpoint: POST https://basetoolbox.cartonpliant.workers.dev/v1/preflight
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-toolbox-uniswap-v3-preflight-check-b8bca918
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_szEkrOC_tGnkjLItdNfrC

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-toolbox-uniswap-v3-preflight-check-b8bca918 -d '<json body>'
```

Example prompt: Before I sign this swap, run a preflight check on Base to see if I can sell my USDC for ETH on Uniswap v3 — tell me the expected output, minimum I'd receive, and any warnings I should know about.

## When to prefer this

Choose this endpoint when you need to validate a Uniswap v3 swap on Base chain before the user signs — particularly when you want to surface warnings, confirm token sellability, or calculate expected output without executing a transaction. Prefer this over on-chain simulation when you want a cheap ($0.10 USDC), fast, pre-packaged preflight that also checks allowances and explains the transaction.

## Known failure modes

- Token not tradeable on Uniswap v3 Base — sellable: false
- Insufficient liquidity for the requested trade size
- Payment not received or invalid USDC payment — 402 response
- Malformed input object missing required swap parameters
- Slippage or price impact too high — warning in warnings array
- Token contract address not recognized on Base network

## How this service works

Base toolbox: before you sign on Base — Uniswap v3 preflight, leftover allowances, tx explain, transfer check. $0.10 USDC. Also $0.001 price/gas/ENS. GET /v1/constants free. No CoinGecko key.

## Output

A JSON object indicating whether the swap is safe to proceed (ok), the recommended next action (next), expected output amount (amountOut), minimum acceptable output (minOut), whether the token is sellable (sellable), and an array of any warnings about the transaction.

## Request schema (JSON Schema)

```json
{
 "properties": {
  "input": {
   "type": "object"
  },
  "output": {
   "type": "object"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "next": "swap",
  "minOut": "…",
  "sellable": true,
  "warnings": [],
  "amountOut": "…"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-toolbox-uniswap-v3-preflight-check-b8bca918/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from basetoolbox.cartonpliant.workers.dev](https://www.zero.xyz/host/basetoolbox.cartonpliant.workers.dev/llms.txt)