Guide · x402

A procedure for designing agent workflows that resist prompt injection: mapping which t…

by Saylor Innovations Knowledge Base · verified provider · updated 2026-09-22

What it does

A procedure for designing agent workflows that resist prompt injection: mapping which tools/credentials/side effects an untrusted content source can reach, minimizing and labeling retrieved content by trust/provenance, externalizing policy and authorization into deterministic code rather than the model, using a propose-review-execute pattern for high-impact actions, constraining what untrusted content can write to memory, and running adversarial evaluation (direct, indirect, encoded, cross-tool, exfiltration) measured by unsafe-action rate, not by whether the model mentions the attempt.

Capabilities

Prompt-Injection Defense Guide — a 9-minute technical guide

Tags: security & opsec · advanced · prompt-injection · agent-security · llm-security · tool-authorization · owasp

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/prompt-injection-defense.json for the price and payment options.
Pay. Call GET https://saylorinnovations.com/api/kb?id=prompt-injection-defense. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC or USDT on Solana, Base, Polygon, Arbitrum One, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.01 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Solana, Base, Polygon, Arbitrum One

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp	USDC	$0.01	7LSjfrJf8fNsB8VA9u7N3WEn25smQLpob3SvyUvXacy7	120s
exact	Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp	USDT	$0.01	7LSjfrJf8fNsB8VA9u7N3WEn25smQLpob3SvyUvXacy7	120s
exact	Base eip155:8453	USDC	$0.01	0xf8A376eBF123D7252cd7b66bcD77A727a4def22f	120s
exact	Polygon eip155:137	USDC	$0.01	0xf8A376eBF123D7252cd7b66bcD77A727a4def22f	120s
exact	Arbitrum One eip155:42161	USDC	$0.01	0xf8A376eBF123D7252cd7b66bcD77A727a4def22f	120s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "payTo": "7LSjfrJf8fNsB8VA9u7N3WEn25smQLpob3SvyUvXacy7",
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "amount": "10000",
    "amountUsd": 0.01,
    "maxTimeoutSeconds": 120
  },
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "payTo": "7LSjfrJf8fNsB8VA9u7N3WEn25smQLpob3SvyUvXacy7",
    "asset": "Es9vMFrzaCERmJfrF4H2FYD4KCoNkY11McCe8BenwNYB",
    "amount": "10000",
    "amountUsd": 0.01,
    "maxTimeoutSeconds": 120
  },
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xf8A376eBF123D7252cd7b66bcD77A727a4def22f",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "amountUsd": 0.01,
    "maxTimeoutSeconds": 120
  },
  {
    "scheme": "exact",
    "network": "eip155:137",
    "payTo": "0xf8A376eBF123D7252cd7b66bcD77A727a4def22f",
    "asset": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359",
    "amount": "10000",
    "amountUsd": 0.01,
    "maxTimeoutSeconds": 120
  },
  {
    "scheme": "exact",
    "network": "eip155:42161",
    "payTo": "0xf8A376eBF123D7252cd7b66bcD77A727a4def22f",
    "asset": "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
    "amount": "10000",
    "amountUsd": 0.01,
    "maxTimeoutSeconds": 120
  }
]

Examples

curl

curl "https://saylorinnovations.com/api/kb?id=prompt-injection-defense"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://saylorinnovations.com/api/kb?id=prompt-injection-defense");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
res = httpx.get("https://saylorinnovations.com/api/kb?id=prompt-injection-defense")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: Saylor Innovations Knowledge Base
Endpoint: https://saylorinnovations.com/api/kb?id=prompt-injection-defense
License: LicenseRef-Saylor-Agent-Use-1.0
Machine-readable: /resources/prompt-injection-defense.json