# FastPath API – Bitcoin Template Batch Check

> FastPath API – Bitcoin Template Batch Check is a paid API for AI agents from api.nativebtc.org, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-15).

Checks whether a batch of Bitcoin transaction IDs are included in the Core v31 optimized mempool template, given a target block confirmation window.

## Facts

- Endpoint: POST https://api.nativebtc.org/v1/template/batch-check
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastpath-api-bitcoin-template-batch-check-0f23da4d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_hpYplAPnryAwNET4Lwe1S

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 fastpath-api-bitcoin-template-batch-check-0f23da4d -d '<json body>'
```

Example prompt: Can you batch-check whether these 3 Bitcoin txids — 81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325, abc123...def456, and 999aaa...bbb000 — are currently included in the Core v31 optimized block template, targeting confirmation within 3 blocks?

## When to prefer this

Use this endpoint when you need to batch-verify whether specific Bitcoin transactions are included in Bitcoin Core v31's optimized block template, particularly when making RBF-bump or fee decisions, verifying settlement batches, or monitoring near-term confirmation likelihood. Prefer this over single-transaction mempool lookups when you have up to 10 txids to check simultaneously. It is distinct from general mempool fee estimation — this specifically checks template inclusion status via the Core v31 optimizer cache.

## Known failure modes

- Invalid txid format (not 64 hex characters) returns a validation error
- Exceeding 10 txids in a single batch returns a schema violation error
- targetBlocks below 1 rejected as invalid
- Payment failure via x402 protocol returns 402 Payment Required
- txid not found in mempool may return inOptimizedTemplate: false without explicit error
- Temporary Core node unavailability may return a non-success response

## How this service works

FastPath translates Ethereum-style JSON-RPC requests into Bitcoin data, fee intelligence, mempool insight, and Core v31 package signals. Paid by x402.

## Output

Returns a JSON object with a mode field (e.g. 'live_cached'), source identifier (e.g. 'core_v31_optimizer_cache'), a results array where each entry contains the txid and a boolean 'inOptimizedTemplate' flag, an 'included' count, and a 'success' boolean.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "txids": {
   "type": "array",
   "items": {
    "type": "string",
    "pattern": "^[0-9a-fA-F]{64}$",
    "description": "Bitcoin transaction ID as 64 lowercase or uppercase hex characters."
   },
   "maxItems": 10,
   "minItems": 1
  },
  "targetBlocks": {
   "type": "number",
   "minimum": 1,
   "description": "Desired confirmation target in blocks."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "mode": "live_cached",
  "source": "core_v31_optimizer_cache",
  "results": [
   {
    "txid": "81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325",
    "inOptimizedTemplate": true
   }
  ],
  "success": true,
  "included": 1
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastpath-api-bitcoin-template-batch-check-0f23da4d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.nativebtc.org](https://www.zero.xyz/host/api.nativebtc.org/llms.txt)