# TzKT Balance History at Block

> TzKT Balance History at Block is a paid API for AI agents from x402.tzkt.io, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Retrieves the historical balance of a Tezos account at a specific blockchain block level

## Facts

- Endpoint: POST https://x402.tzkt.io/v1/accounts/%7Baddress%7D/balance_history/%7Blevel%7D
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/tzkt-balance-history-at-block-249e3e74
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_up4kvN5Ngi9si7x5_F6vX

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 tzkt-balance-history-at-block-249e3e74 -d '<json body>'
```

Example prompt: What was the XTZ balance of the Tezos account tz1VSUr8wwNhLAzempoch5d6hLRiTh8Cjcjb at block level 5200000?

## When to prefer this

Use this endpoint when you need a precise point-in-time balance for a Tezos account at a specific block height — ideal for auditing, portfolio snapshots, tax calculations, or verifying balances at historical moments. Prefer over general account endpoints when the exact block-level granularity matters. No API key required, just micro-payment via x402.

## Known failure modes

- Invalid or malformed Tezos address returns 400 Bad Request
- Block level does not exist yet or is in the future returns 404 or empty result
- Network connectivity issues to x402.tzkt.io return 5xx errors
- Payment of 0.002 USDC via x402 protocol not provided returns 402 Payment Required
- Address that never existed on-chain may return zero balance

## How this service works

TzKT is a comprehensive Tezos blockchain indexer API. Access blocks, operations, accounts, contracts, bigmaps, delegates, tokens and network stats through a fast REST API. No signup or API key required.

## Output

Returns the account's balance in mutez (micro-tez) at the specified block level, representing a historical snapshot of that address's holdings at that precise point in the Tezos blockchain.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/tzkt-balance-history-at-block-249e3e74/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.tzkt.io](https://www.zero.xyz/host/x402.tzkt.io/llms.txt)