agentic-payments

A guide to x402 and MPP, protocols for letting software agents and machines pay for online APIs using Stellar and USDC, a digital dollar token.

In plain words
What is it for?
Use it to sell or call paid APIs, support fee-sponsored clients, handle frequent agent payments, or help agents discover payable services.
Why use it?
It helps choose between one-payment-per-request and session-based payment flows, including whether a payment facilitator is needed.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/stellar/stellar-dev-skill/agentic-payments
Any agent
npx skills add stellar/stellar-dev-skill --skill agentic-payments
Clone the repo
git clone --depth 1 https://github.com/stellar/stellar-dev-skill

Made for: Claude Code, Codex.

Per session 125 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,752 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
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 $0.00125 $0.01752
Opus 5 $0.00063 $0.00876
Sonnet 5 $0.00025 $0.00350
Haiku 4.5 $0.00013 $0.00175

Measured 2d ago against content hash 2af48a37773b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

agentic-payments scanned grade A with 1 finding 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 2d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl "https://friendbot.stellar.org?addr=RECIPIENT_G..."
skills/agentic-payments/SKILL.md · 119 lines

How it starts

The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agentic Payments: x402 + MPP

Two complementary protocols for AI-agent and machine-to-machine payments on Stellar. Pick based on who depends on whom and how often the agent pays.

Quick decision

x402 MPP Charge MPP Session
Per-request on-chain tx? Yes (via facilitator) Yes (SAC) No (off-chain commits)
Needs facilitator? Yes (OZ Channels) No No
Client needs XLM? No (fees sponsored) Optional (feePayer) Yes
Setup complexity Low Low Medium (deploy contract first)
Best for Quickest setup, fee-free clients No third-party dep High-frequency agents
  • Selling an API, want zero-XLM clients → x402 Seller in x402.md
  • Calling an x402 API from an agent → x402 Buyer in x402.md
  • Selling an API, no facilitator dependency → Charge mode in mpp.md
  • Agent making many requests per session → Session mode in mpp.md
  • Sold an API, now want agents to find it → Discovery in mpp.md
  • Unsure → x402 (lowest friction to get started)

All protocols use USDC (SEP-41 SAC) by default; stellar:testnet / stellar:pubnet CAIP-2 network IDs.

Read the file that matches the task

This file carries the decision table, the shared testnet account setup, and the USDC address reference. The protocol playbooks live alongside it:

Task File
Sell a paid API via a facilitator (zero-XLM clients), build an x402 buyer agent x402.md
Facilitator-free per-request payments (Charge) or channel-backed sessions (Session) mpp.md
Publish an OpenAPI discovery document so agents find your paid API Discovery
Create/fund testnet accounts, add USDC trustlines, get testnet USDC Testnet setup (below)
Which USDC address goes where (classic issuer vs SAC) Two USDC addresses (below)

Read the full file on GitHub · 119 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 2d ago First seen · 119 lines · 125 tokens per session scan A 2af48a37773b

Subscribe to this mod's changes

agentic-payments is a skill published in the GitHub repository stellar/stellar-dev-skill (51 stars, last pushed 4d ago), licensed Apache-2.0. It adds 125 tokens to every session and 1,752 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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