# Nomos Execution Environment Preflight API

> Nomos Execution Environment Preflight API is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $2/call, status unknown (last checked 2026-09-14).

Assesses the risk level and flags of a code execution action within a specified environment before an autonomous agent proceeds with execution.

## Facts

- Endpoint: POST https://base-agent-preflight.bytoken2023.workers.dev/x402/v1/execution/environment-preflight
- Price: $2/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nomos-execution-environment-preflight-api-c4027a05
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1HRrJ40n_RDqPfqkaPV_X

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-execution-environment-preflight-api-c4027a05 -d '<json body>'
```

Example prompt: Before you run that code, do an execution environment preflight check using Nomos to assess the risk level and any flags for a CODE_EXECUTION action in my current environment — I want to make sure it's safe to proceed.

## When to prefer this

Choose this endpoint when an autonomous agent needs to gate code execution behind a risk assessment step — especially in agentic pipelines where safety and compliance are required before proceeding. Prefer this over generic health checks when you specifically need a structured risk_score, risk_level enum, and flags array scoped to code execution actions on a target environment.

## Known failure modes

- Invalid or missing action type returns a validation error
- Unknown or unsupported environment identifier may return an error or elevated risk score
- Payment failure (insufficient USDC) blocks the request with a 402 response
- Malformed request body causes a 400 error
- Service unavailability on Cloudflare Workers returns a 503

## 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

Returns a JSON object containing the network identifier (e.g. eip155:8453), product name, and an assessment object with a risk_level (e.g. 'low'), a numeric risk_score, and a flags array listing any detected risks or concerns about the execution environment.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "action": {
   "type": "CODE_EXECUTION"
  },
  "environment": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "nomos-execution-environment-preflight",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nomos-execution-environment-preflight-api-c4027a05/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)