Guard Shell
by ShellPermit in Developer tools
Decide whether an agent-authored bash command complies with an execution policy, using a real shell tokenizer rather than pattern matching. Catches recursive deletes, force pushes, cluster and infrastructure teardown, raw device writes, path escapes, privilege escalation, and curl-piped-to-shell through pipelines, substitutions, quoting games and base64. Returns reason codes with spans and an optional short-lived permit bound to the exact canonical command. Never executes anything.
https://shellpermit.schemasure.com/v1/guard/shell- Price
- $0.03
- per call in USDC
- Uptime
- 100%
- last 30 days
- Response time
- 359 ms
- 475 ms slowest 5%
- Last check
- Passed
- 1 h ago, next any minute now
Reliability
Status and outage history · Atom feed · Watch with other listings
How to call it
POST https://shellpermit.schemasure.com/v1/guard/shell
Each call costs $0.03 in USDC on Base, paid with the request over x402.
Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.
Example request
From the listing.
POST https://shellpermit.schemasure.com/v1/guard/shell
content-type: application/json
{
"audience": "executor:acme-prod-01",
"command": "rm -rf ./dist && npm run build",
"issue_permit": true,
"policy": {
"allow_destructive": true,
"allow_network_egress": false,
"allowed_roots": [
"/srv/app"
],
"cwd": "/srv/app"
},
"shell": "bash"
}Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
audience | string | No | Identity of the ONE executor the permit is for. Required when issue_permit is true. Wildcards are rejected. |
command | string | Yes | |
env | object | No | Environment the executor will run with, used only for static expansion so that paths like "$HOME/.cache" can be resolved and decided rather than reported as unresolvable. |
issue_permit | boolean | No | |
policy | object | No | |
shell | string | Yes | Required. Only bash is supported in v1: a permit issued under one shell's grammar and executed under another is a parser differential with a signature on it. One of: bash. |
subject | string | No | Opaque caller label recorded as the permit subject. |
Example response
The provider's example. We can't check it without paying.
{
"confidence": 1,
"evidence": [],
"ok": true,
"result": {
"canonical_command": "rm -f -r ./dist && npm run build",
"cmd_fingerprint": "a1b2c3d4e5f60718",
"cmd_hash": "sha256:0f4c…1c2d",
"permit": "eyJhbGciOiJFZDI1NTE5Iiwia2lkIjoi…"
},
"risk_codes": [],
"verdict": "pass",
"warnings": [
"cmd_fingerprint is ADVISORY and must not be used for authorization."
]
}Call it from code
The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.03.
curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://shellpermit.schemasure.com/v1/guard/shell' \
-H 'content-type: application/json' \
--data-raw '{"audience":"executor:acme-prod-01","command":"rm -rf ./dist && npm run build","issue_permit":true,"policy":{"allow_destructive":true,"allow_network_egress":false,"allowed_roots":["/srv/app"],"cwd":"/srv/app"},"shell":"bash"}'
# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://shellpermit.schemasure.com/v1/guard/shell' \
-H 'content-type: application/json' \
--data-raw '{"audience":"executor:acme-prod-01","command":"rm -rf ./dist && npm run build","issue_permit":true,"policy":{"allow_destructive":true,"allow_network_egress":false,"allowed_roots":["/srv/app"],"cwd":"/srv/app"},"shell":"bash"}' \
| grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decodeJavaScript: pay and call
// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";
// Pays at most $0.03 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.03" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);
// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.03 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fshellpermit.schemasure.com%2Fv1%2Fguard%2Fshell&method=POST
const res = await pay("https://shellpermit.schemasure.com/v1/guard/shell", {
method: "POST",
headers: { "content-type": "application/json" },
body: JSON.stringify({
"audience": "executor:acme-prod-01",
"command": "rm -rf ./dist && npm run build",
"issue_permit": true,
"policy": {
"allow_destructive": true,
"allow_network_egress": false,
"allowed_roots": [
"/srv/app"
],
"cwd": "/srv/app"
},
"shell": "bash"
}),
});
console.log(res.status, await res.text());Python: pay and call
# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client
# Pays at most $0.03 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.03"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))
with x402_requests(client) as session:
res = session.post(
"https://shellpermit.schemasure.com/v1/guard/shell",
json={
"audience": "executor:acme-prod-01",
"command": "rm -rf ./dist && npm run build",
"issue_permit": True,
"policy": {
"allow_destructive": True,
"allow_network_egress": False,
"allowed_roots": [
"/srv/app",
],
"cwd": "/srv/app",
},
"shell": "bash",
},
)
print(res.status_code, res.text)Security scan
No findings
We scan names, descriptions and tool definitions for hidden instructions and other prompt-injection patterns.
Recent checks
| When | Result | HTTP | Time | Price |
|---|---|---|---|---|
| 1 h ago | Passed | 402 | 345 ms | $0.03 |
| 6 h ago | Passed | 402 | 642 ms | $0.03 |
| 11 h ago | Passed | 402 | 316 ms | $0.03 |
| 15 h ago | Passed | 402 | 374 ms | $0.03 |
| 20 h ago | Passed | 402 | 438 ms | $0.03 |
Show 10 older checks
| 25 h ago | Passed | 402 | 359 ms | $0.03 |
| 29 h ago | Passed | 402 | 333 ms | $0.03 |
| 34 h ago | Passed | 402 | 326 ms | $0.03 |
| 38 h ago | Passed | 402 | 398 ms | $0.03 |
| 42 h ago | Passed | 402 | 372 ms | $0.03 |
| 46 h ago | Passed | 402 | 475 ms | $0.03 |
| 2 days ago | Passed | 402 | 332 ms | $0.03 |
| 2 days ago | Passed | 402 | 353 ms | $0.03 |
| 2 days ago | Passed | 402 | 433 ms | $0.03 |
| 3 days ago | Passed | 402 | 339 ms | $0.03 |