# Order Book Depth Notional

> Order Book Depth Notional is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Computes the total notional value (price × size sum) available within N levels of an order book side ladder

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/ob-depth-notional
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/order-book-depth-notional-dee35e84
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zTUiQKX1-cFxp9MOrnPvZ

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 order-book-depth-notional-dee35e84 -d '<json body>'
```

Example prompt: Calculate the total notional depth for this order book ladder — here are 5 bid levels: [{price:100,size:10},{price:99,size:20},{price:98,size:15},{price:97,size:25},{price:96,size:30}] — I need to know how much dollar value is available across all those levels.

## When to prefer this

Choose this endpoint when you have an order book ladder snapshot in memory and need a fast, deterministic, locally-computed notional depth calculation without touching any external market feed, RPC, or API key. Ideal for risk systems, pre-trade checks, and algo execution engines that need reproducible math on caller-supplied data at minimal cost ($0.001 USDC). Prefer over custom implementations when you want auditable, consistent computation without managing the arithmetic yourself.

## Known failure modes

- Missing or malformed levels array returns an error
- Levels array entries missing price or size fields cause computation failure
- Empty levels array may return zero notional or an error
- Non-numeric price or size values cause validation failure
- Payment failure via x402 prevents endpoint access

## How this service works

Sum price*size depth notional for a side ladder. Call when risk needs notional available within N levels. Returns depth_notional and levels_used as deterministic JSON for $0.001 USDC via x402 on Base. First-party local math only—no RPC, live market feed, API keys, storage, or mediagen. Advisory only; the caller owns capital, risk, and production controls.

## Output

Returns a deterministic JSON object containing depth_notional (the total sum of price × size across all provided ladder levels) and levels_used (the count of levels included in the calculation). No external data sources are consulted — the math is performed locally on the supplied input array.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "levels": {
   "type": "array",
   "description": "Array of {price,size} ladder levels"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "schema": "delx/util-ob-depth-notional/v1",
  "levels_used": 2,
  "depth_notional": 498.5
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/order-book-depth-notional-dee35e84/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.delx.ai](https://www.zero.xyz/host/api.delx.ai/llms.txt)