# B20 Memo Event History Reader

> B20 Memo Event History Reader is a paid API for AI agents from 402.com.tr, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-14).

Reads on-chain Memo event history for a B20 token, optionally filtered by a specific memo (bytes32) or caller wallet, enabling payment settlement reconciliation.

## Facts

- Endpoint: GET https://402.com.tr/api/x402/b20-memo
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/b20-memo-event-history-reader-2bd404cd
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_2PdMjLwNWDv2f44f9oD86

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 b20-memo-event-history-reader-2bd404cd
```

Example prompt: Pull the full on-chain memo event history for the B20 token at address 0xAbC123... on Base — filter it down to only events from the wallet 0xDef456... so I can reconcile which payments went through.

## When to prefer this

Use this endpoint when you need to reconcile or audit B20 stablecoin payments by their on-chain memo field — specifically when payment IDs, compliance tags, or settlement correlation keys were embedded in transferWithMemo calls. This is the only primitive for reading the memo event log that ERC-20 lacks natively. Prefer this over general blockchain explorers when you want structured, filtered memo history for agent-driven settlement workflows.

## Known failure modes

- Invalid or non-B20 token address returns an error or empty result
- Non-hex or malformed bytes32 memo string causes a query parse error
- Caller wallet address in wrong format (non-checksummed or invalid) returns a validation error
- Token has no Memo events emitted — returns empty array
- Network congestion on Base may cause delayed or stale event reads
- Payment of $0.03 USDC not settled causes request rejection

## How this service works

🆕 B20 adds memos to transfers/mints/burns (transferWithMemo) for payment IDs, compliance tags and settlement correlation — a field ERC-20 has no equivalent for. Reads a token's on-chain Memo event history, optionally filtered by a specific memo (bytes32) or the caller wallet. The settlement-reconciliation primitive for agents paying over B20 stablecoins.

## Output

Returns a list of on-chain Memo events emitted by the B20 token contract, each containing the memo (bytes32 payload used as payment ID, compliance tag, or settlement correlation key), the caller wallet, and associated transfer metadata. Results are optionally scoped to a specific memo value or caller wallet.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "memo": {
       "type": "string",
       "description": "Filter by memo (bytes32, optional)"
      },
      "caller": {
       "type": "string",
       "description": "Filter by caller wallet (optional)"
      },
      "address": {
       "type": "string",
       "description": "B20 token address"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/b20-memo-event-history-reader-2bd404cd/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 402.com.tr](https://www.zero.xyz/host/402.com.tr/llms.txt)