# SALT19 Base Token Allowance Lookup

> SALT19 Base Token Allowance Lookup is a paid API for AI agents from api.salt19.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Returns the current ERC-20 token allowance granted by an owner address to a spender address on the Base network

## Facts

- Endpoint: POST https://api.salt19.com/v1/base-token-allowance
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/salt19-base-token-allowance-lookup-c6f3f250
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8hPTxBRNuheCvVvmMaT77

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 salt19-base-token-allowance-lookup-c6f3f250 -d '<json body>'
```

Example prompt: What is the current ERC-20 token allowance that owner 0xAbC1234567890AbC1234567890AbC1234567890Ab has granted to spender 0xDeF0987654321DeF0987654321DeF0987654321De for the token at 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base?

## When to prefer this

Choose this endpoint when you need on-chain ERC-20 allowance data specifically on the Base network (eip155:8453) and want a simple pay-per-call REST interface without managing your own RPC infrastructure. Particularly useful for AI agents in the SALT19/EvoMind ecosystem that need to verify approval state before executing DeFi actions, or for pre-flight checks before token transfers.

## Known failure modes

- Invalid Ethereum address format (must be 0x-prefixed 40 hex chars) returns a validation error
- Token address not found or not an ERC-20 contract may return zero or an error
- Network congestion or RPC node unavailability may cause timeouts
- Payment of $0.01 USDC not received results in 402 Payment Required response
- Malformed JSON body returns a 400 Bad Request

## How this service works

SALT19 is an independent applied AI systems lab behind EvoMind governed cognition, the MCP-native Agent Utility Grid, the ARCS research community, AeroClear UAS flight intelligence, and practical software for real-world work.

## Output

Returns a JSON object containing the network identifier (eip155:8453 for Base), the block number at which the allowance was read, and the allowance amount in atomic (smallest) units as a string. A value of '0' means no approval has been granted.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "owner": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  },
  "spender": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  },
  "token_address": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "block_number": 12345678,
  "allowance_atomic": "0"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/salt19-base-token-allowance-lookup-c6f3f250/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.salt19.com](https://www.zero.xyz/host/api.salt19.com/llms.txt)