# Nomos ETH/USD Value Assessment API

> Nomos ETH/USD Value Assessment API is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Returns the current ETH/USD exchange rate with associated risk assessment, network metadata, and risk scoring via a pay-per-request preflight API.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/x402/v1/value/eth-usd
- 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/nomos-eth-usd-value-assessment-api-d9b4be8c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nGpDXFGomsIjaJNWvrC0S

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 nomos-eth-usd-value-assessment-api-d9b4be8c
```

Example prompt: What is the current ETH/USD price along with its risk score and any flags — I want to check it's safe before my agent uses it for a conversion calculation?

## When to prefer this

Choose this endpoint when an AI agent needs a risk-assessed, network-aware ETH/USD price feed — particularly for preflight checks before on-chain transactions or agent-executed payments on Base. It is distinct from bare price APIs because it bundles a risk score and flags alongside the price, making it suitable for autonomous decision gates rather than just display.

## Known failure modes

- Invalid amount format (non-numeric or negative) returns 400 with validation error
- Missing or failed x402 payment returns 402 Payment Required
- Network or Cloudflare Worker downtime returns 503
- Price feed unavailability may return 503 or a stale/error response
- Malformed query parameter (e.g. amount with too many decimal places) returns 400

## How this service works

Machine-payable service intelligence for discovering, verifying, and monitoring identity, risk, authorization, execution-preflight, and evidence APIs before autonomous agents spend.

## Output

A JSON object containing the network identifier (e.g. eip155:8453 for Base), the product name ('nomos-value-eth-usd'), and an assessment object with a risk_score (numeric), risk_level (e.g. 'low'), and a flags array (empty when clean). Optionally includes activity, identity, and provenance objects depending on the request.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "amount": {
       "type": "string",
       "pattern": "^[0-9]+(?:\\.[0-9]{1,18})?$",
       "description": "Optional positive decimal ETH amount. Defaults to 1."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "network": {
       "type": "string"
      },
      "product": {
       "type": "string"
      },
      "activity": {
       "type": "object"
      },
      "identity": {
       "type": "object"
      },
      "assessment": {
       "type": "object"
      },
      "provenance": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "nomos-value-eth-usd",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nomos-eth-usd-value-assessment-api-d9b4be8c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-agent-preflight.bytoken2023.workers.dev](https://www.zero.xyz/host/base-agent-preflight.bytoken2023.workers.dev/llms.txt)