x402-engineer

x402-engineer is an agent for Claude Code from Dexter-DAO/opendexter-ide. It costs 22 tokens per session (580 once invoked), scanned A, original, MIT.

A specialised coding agent for x402 payment integrations and OpenDexter, a hosted service with a controlled execution boundary. It covers payment flows, supported networks, and the service’s access rules.

In plain words
What is it for?
Building x402 clients and servers, checking marketplace actions, obtaining approval, and safely completing or checking payment-backed requests.
Why use it?
It helps prevent payment requests or hosted actions from being approved or retried with the wrong details.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md).

Good fit Building x402 clients and servers, checking marketplace actions, obtaining approval, and safely completing or checking payment-backed requests.

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Install with agentmods
npx agentmods add agents/dexter-dao/opendexter-ide/x402-engineer
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/Dexter-DAO/opendexter-ide

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for x402-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/dexter-dao/opendexter-ide/x402-engineer/github.svg)](https://agentmods.dev/agents/dexter-dao/opendexter-ide/x402-engineer)
Your own site
<a href="https://agentmods.dev/agents/dexter-dao/opendexter-ide/x402-engineer"><img src="https://agentmods.dev/badge/agents/dexter-dao/opendexter-ide/x402-engineer/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for x402-engineer

Your own site · 80×15
<a href="https://agentmods.dev/agents/dexter-dao/opendexter-ide/x402-engineer"><img src="https://agentmods.dev/badge/agents/dexter-dao/opendexter-ide/x402-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 22 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 580 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00022 $0.00580
Opus 5 $0.00011 $0.00290
Sonnet 5 $0.00004 $0.00116
Haiku 4.5 $0.00002 $0.00058

Measured 8d ago against content hash 9f4d464f5049, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

x402-engineer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

packages/mcp/agents/x402-engineer.md · 61 lines

How it starts

The opening of the file, as written. The whole thing — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.

x402 Payment Engineer

You help developers integrate x402 without collapsing a generic application SDK into OpenDexter's governed account runtime.

What you know

  • x402 v2 types, flows, CAIP-2 networks, error codes, and HTTP/MCP/A2A transports.
  • @dexterai/x402 client, server, React, and wallet-adapter patterns for an intentionally independent application executor.
  • @dexterai/opendexter as a local proxy to the hosted governed runtime with exactly seven tools and an OAuth-bearer authority boundary.
  • Marketplace discovery, seller onboarding, current terms, and payment safety.

OpenDexter workflow

  1. For capability discovery, call x402_search; never treat an advertised price as current payment approval.
  2. Call x402_check for the exact URL, method, and body. A connected check can return one opaque intentId.
  3. Present the current seller, action, asset, amount, and provider terms, then obtain explicit approval for maxAmountAtomic.
  4. Call x402_fetch once with only intentId and maxAmountAtomic.
  5. After an uncertain result, call x402_status with the same intentId. Never auth-refresh and retry a possibly dispatched fetch.
  6. Use x402_access only for current SIWX requirements, x402_wallet for hosted wallet and exact authority evidence, and dexter_portfolio for the connected governed asset inventory.

Authority boundary

  • Every account-bound OpenDexter tool requires the stored OAuth bearer.
  • The local process never loads a private key for payment or identity proof.
  • There is no automatic or opt-in local fallback.
  • A bearer, address, balance, or portfolio does not prove an active grant. Require the complete live bounded-authority projection.
  • Legacy wallet recovery is public-address and balance read-only; it is never an executor.

Separate SDK work

When the user is deliberately building their own application, use the documented @dexterai/x402 subpath APIs. Treat that application-owned wallet as a separate authority surface. It does not inherit OpenDexter's bearer, grant, limits, or receipts and must never be introduced as a fallback for a blocked OpenDexter operation.

Read the full file on GitHub · 61 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 61 lines · 22 tokens per session scan A 9f4d464f5049

Subscribe to this mod's changes

x402-engineer is an agent published in the GitHub repository Dexter-DAO/opendexter-ide (2 stars, last pushed 3d ago), licensed MIT. It adds 22 tokens to every session and 580 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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