# Nomos Agent Action Preflight Check

> Nomos Agent Action Preflight Check is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Evaluates an agent's proposed action (tool call, shell command, wallet operation, etc.) for identity, risk, and authorization before execution.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/agent/action-preflight
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nomos-agent-action-preflight-check-5731d79d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_RnWmlS5yvcHjrvBLBcTku

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-agent-action-preflight-check-5731d79d
```

Example prompt: Before my agent executes a wallet action targeting 'usdc-transfer.example.com' in the production environment involving 50.00 USDC, run a preflight risk check and tell me the risk level and any flags.

## When to prefer this

Use this endpoint when an autonomous agent needs a real-time, pay-per-use preflight gate before executing any side-effecting action — especially wallet operations, shell commands, deployments, or external API calls. Prefer it over static rule engines when you need dynamic risk scoring with identity and provenance context baked in, and when operating on the Base blockchain ecosystem with x402 micropayment support.

## Known failure modes

- Missing required query parameters (action_type or target) returns a 400 validation error
- Invalid action_type enum value returns schema validation failure
- Payment not included or insufficient USDC returns 402 Payment Required
- Malformed agent_id pattern (non-alphanumeric) causes parameter rejection
- Extremely high-risk actions may return a 'block' recommendation rather than an error, requiring human_approval_ref

## 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 a risk_level (e.g. 'low', 'medium', 'high'), a numeric risk_score (0–100), a list of flags indicating specific policy concerns, plus optional identity, activity, assessment, and provenance sub-objects describing the evaluated action context.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "action_type",
      "target"
     ],
     "properties": {
      "target": {
       "type": "string",
       "maxLength": 500,
       "minLength": 1,
       "description": "Human-readable target, command, endpoint, domain, or resource."
      },
      "agent_id": {
       "type": "string",
       "pattern": "^[A-Za-z0-9._:-]{1,128}$",
       "description": "Caller-defined agent or principal id."
      },
      "risk_score": {
       "type": "string",
       "pattern": "^[0-9]{1,3}$",
       "description": "Optional caller-supplied 0-100 risk score."
      },
      "action_type": {
       "enum": [
        "tool_call",
        "shell",
        "deploy",
        "dns",
        "email",
        "mcp_call",
        "wallet",
        "x402_purchase",
        "file_write",
        "browser"
       ],
       "type": "string",
       "description": "Side-effecting action the agent wants to run."
      },
      "amount_usdc": {
       "type": "string",
       "pattern": "^[0-9]+(?:\\.[0-9]{1,6})?$",
       "description": "Optional payment, spend, or value at risk."
      },
      "environment": {
       "enum": [
        "local",
        "dev",
        "staging",
        "production",
        "external"
       ],
       "type": "string",
       "description": "Execution environment for the action."
      },
      "human_approval_ref": {
       "type": "string",
       "maxLength": 160,
       "description": "Human approval or ticket reference for elevated actions."
      }
     }
    }
   },
   "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"
      }
 
… (truncated)
```

## Response schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nomos-agent-action-preflight-check-5731d79d/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)