# DropEngine Preflight Action

> DropEngine Preflight Action is a paid API for AI agents from mcp.dropenginehq.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-16).

Pre-screens and validates a wide range of agent intents — tool calls, installs, transactions, claims, and content — before execution, returning a risk assessment and go/no-go signal.

## Facts

- Endpoint: POST https://mcp.dropenginehq.com/api/preflight-action?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/dropengine-preflight-action-52be45c9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vE9wAlvGO5AYOUV93CM5h

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 dropengine-preflight-action-52be45c9 -d '<json body>'
```

Example prompt: Before you send that 0.5 ETH transaction from 0xAbC...123 to 0xDeF...456 on Base, run a preflight check with low risk tolerance to make sure it's safe — the intent is to pay a vendor invoice.

## When to prefer this

Choose this endpoint when an autonomous agent needs a unified pre-execution safety gate before performing any consequential action — including blockchain transactions, MCP tool calls, URL fetches, npm installs, content verification, or invoice checks. It is the single-endpoint alternative to calling multiple specialized preflight services individually, and is especially valuable when the agent must enforce a configurable risk tolerance before acting.

## Known failure modes

- Intent string too short or missing (minLength:3 violation)
- Target URL malformed or exceeds 4096 characters
- Wallet address does not match 0x hex pattern
- Token object missing required chain or token_address fields
- Transaction object missing required fields (chain, from, to, value, data)
- Unsupported action_type enum value
- Content exceeds 100,000 character limit
- Service unavailable or payment not processed (x402 payment required)

## How this service works

Discover pay-per-call MCP services for agent security, web research, product data, invoice checks, blockchain risk and crypto analysis. Base USDC via x402.

## Output

Returns a structured preflight verdict including a risk assessment, a go/no-go recommendation, and any flags or discrepancies found — such as wallet risk indicators, claim mismatches, unsafe URL patterns, or package vulnerabilities — scoped to the specific action type and target provided.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "intent": {
   "type": "string",
   "maxLength": 500,
   "minLength": 3
  },
  "target": {
   "type": "object",
   "default": {},
   "properties": {
    "url": {
     "type": "string",
     "format": "uri",
     "maxLength": 4096
    },
    "tool": {
     "type": "string",
     "maxLength": 128,
     "minLength": 1
    },
    "claim": {
     "type": "string",
     "maxLength": 2000,
     "minLength": 3
    },
    "token": {
     "type": "object",
     "required": [
      "chain",
      "token_address"
     ],
     "properties": {
      "chain": {
       "type": "string",
       "maxLength": 32
      },
      "token_address": {
       "type": "string",
       "maxLength": 128
      }
     },
     "additionalProperties": false
    },
    "wallet": {
     "anyOf": [
      {
       "type": "string",
       "pattern": "^0x[a-fA-F0-9]{40}$"
      },
      {
       "type": "object",
       "required": [
        "address"
       ],
       "properties": {
        "chain": {
         "enum": [
          "base",
          "base-sepolia"
         ],
         "type": "string",
         "default": "base"
        },
        "address": {
         "type": "string",
         "pattern": "^0x[a-fA-F0-9]{40}$"
        }
       },
       "additionalProperties": false
      }
     ]
    },
    "content": {
     "type": "string",
     "maxLength": 100000,
     "minLength": 1
    },
    "package": {
     "type": "string",
     "maxLength": 214,
     "minLength": 1
    },
    "capability": {
     "type": "string",
     "maxLength": 80,
     "minLength": 2
    },
    "transaction": {
     "type": "object",
     "required": [
      "chain",
      "from",
      "to",
      "value",
      "data"
     ],
     "properties": {
      "to": {
       "type": "string",
       "maxLength": 128
      },
      "data": {
       "type": "string",
       "maxLength": 200000
      },
      "from": {
       "type": "string",
       "maxLength": 128
      },
      "chain": {
       "type": "string",
       "maxLength": 32
      },
      "value": {
       "type": "string",
       "maxLength": 128
      }
     },
     "additionalProperties": false
    },
    "content_type": {
     "enum": [
      "text",
      "html",
      "markdown",
      "email",
      "tool_output",
      "api_response",
      "document_text"
     ],
     "type": "string"
    },
    "mcp_endpoint": {
     "type": "string",
     "format": "uri",
     "maxLength": 2048
    },
    "extract_field
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/dropengine-preflight-action-52be45c9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mcp.dropenginehq.com](https://www.zero.xyz/host/mcp.dropenginehq.com/llms.txt)