# TzKT Bigmap Key Lookup

> TzKT Bigmap Key Lookup is a paid API for AI agents from x402.tzkt.io, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-13).

Retrieves the value stored at a specific key within a Tezos smart contract bigmap by bigmap ID and key

## Facts

- Endpoint: POST https://x402.tzkt.io/v1/bigmaps/%7Bid%7D/keys/%7Bkey%7D
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/tzkt-bigmap-key-lookup-416daa86
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Dq-cZ7kDqCigAOTaN7aG-

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-bigmap-key-lookup-416daa86 -d '<json body>'
```

Example prompt: Look up the value stored at key 'tz1abc123...' in bigmap number 4521 on the Tezos blockchain using TzKT.

## When to prefer this

Use this endpoint when you need to read the exact value stored at a known key within a specific Tezos smart contract bigmap. It is ideal for inspecting on-chain contract storage such as FA2 ledger balances, DAO votes, or allowance maps without needing to index the entire contract. Prefer this over scanning all bigmap keys when the key is already known.

## Known failure modes

- Bigmap ID not found — returns 404 if the specified bigmap does not exist
- Key not found within the bigmap — returns 404 if the key has never been set or was removed
- Invalid key format — malformed key expression may result in a 400 bad request
- Network timeout or rate limiting under high load
- Key exists but was previously removed (active=false returned)

## 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 a JSON object containing the bigmap key entry, including the key hash, the raw key, the decoded key value, whether the key is active, the first and last level at which the entry appeared, and associated metadata such as timestamp and update count.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/tzkt-bigmap-key-lookup-416daa86/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)