What is x402-engineer?

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.

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

It helps prevent payment requests or hosted actions from being approved or retried with the wrong details.

x402-engineer — Agent for Claude Code and Cursor by Dexter-DAO

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, Cursor.

Or install opendexter, the plugin that ships this one along with the rest of its 5 skills, 3 commands, 1 agent.

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.

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.

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 750 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.

Model	Per session	Once invoked
Fable 5.1	$0.00022	$0.00750
Opus 5.5	$0.00009	$0.00300
Sonnet 5.5	$0.00004	$0.00150
Haiku 4.5	$0.00002	$0.00075

Measured 7d ago against content hash efe93c098104, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, 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 7d 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 · 75 lines

How it starts

The opening of the file, as written. The whole thing — 75 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 an OAuth-bearer authority boundary. @dexterai/[email protected] exposes eight tools.
Marketplace discovery, seller onboarding, current terms, and payment safety.

OpenDexter workflow

For capability discovery, call x402_search; never treat an advertised price as current payment approval.
Call x402_check for the exact URL, method, and body. A connected check can return one opaque intentId.
Present the current seller, action, asset, amount, and provider terms, then obtain explicit approval for maxAmountAtomic.
Call x402_fetch once with only intentId and maxAmountAtomic.
After an uncertain result, call x402_status with the same intentId. Never auth-refresh and retry a possibly dispatched fetch.
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.

OpenDexter also registers dexter_report_work, including before connection. Use it for meaningful work updates with the stored OAuth bearer bound to the same agent. Reporting needs no spending grant or funding. After rejection or possible dispatch, the proxy does not refresh authentication and resend the report automatically. Keep private data, credentials and control characters out of summaries. Server-assigned observedAt and expiresAt describe statement freshness.

After uncertainty, preserve the same operationId and identical fields. On a revision conflict, inspect currentReport and currentRevision; a deliberate update uses a new operationId and that currentRevision as expectedRevision. Financial outcomes retain their own receipts.

Read the full file on GitHub · 75 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.

7d ago Changed efe93c098104
1mo ago Changed · +14 lines 81f045dc7f2d
2mo 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 8d ago), licensed MIT. It adds 22 tokens to every session and 750 once invoked, about $0.0001 per session on Opus 5.5. 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.

Building agents Finance and fintech agents ai ai-agents cursor ide-plugin x402

x402-engineer next to 6 agents from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
x402-engineerDexter-DAO/opendexter-ide	Agent	2	8d ago	MIT	A	22	Claude Code, Cursor
portfolio-review-reminderdaddia/claude-for-strategy	Agent	2	4mo ago	MIT	A	31	Claude Code
criticcodecast-sh/codecast	Agent	43	yesterday	MIT	A	28	Claude Code
monetization-experttravisjneuman/.claude	Agent	107	yesterday	MIT	A	18	Claude Code
devops-engineerfaizkhairi/claude-code-blueprint	Agent	73	yesterday	MIT	A	29	Claude Code
stock-balance-sheet-reviewerjohnqtcg/awesome-skills	Agent	30	28d ago	MIT	A	94	Claude Code
stock-earnings-quality-reviewerjohnqtcg/awesome-skills	Agent	30	28d ago	MIT	A	105	Claude Code