Glossary

Key terms in AI agent payments, the x402 protocol, and autonomous agent infrastructure.

A

Agent Wallet

A blockchain wallet assigned to an AI agent, managed by Mithril, with configurable spending limits and controls.

AI Agent

An autonomous software system powered by a large language model that can take actions, use tools, and make decisions to accomplish goals.

API Key

A secret credential used to authenticate with an API service — the traditional model that x402 aims to replace for agent-to-service interactions.

API Marketplace

A curated directory of APIs that AI agents can discover, evaluate, and pay for on a per-call basis.

Autonomous Spending

The ability of an AI agent to make financial decisions and execute payments without human approval for each transaction.

B

Base

A Layer 2 blockchain built on Ethereum by Coinbase, offering low fees and fast settlement — the default chain for Mithril payments.

Billing Cycle

The monthly period during which agent spending accrues, followed by a statement and a 21-day payment window at zero interest.

C

Credit Line

A revolving line of credit issued to an agent or team by Mithril, enabling agents to spend now and settle at the end of the billing cycle.

G

Gas Fees

The transaction fees paid to blockchain validators for processing on-chain operations like USDC transfers.

H

HTTP 402 Payment Required

An HTTP status code reserved for future use since 1997, now used by x402 to signal that a request requires payment before processing.

L

LLM (Large Language Model)

A neural network trained on vast text data that powers AI agents' reasoning, planning, and decision-making capabilities.

M

MCP (Model Context Protocol)

An open protocol by Anthropic that lets AI models connect to external tools, data sources, and services through a standardized interface.

Micro-Transaction

A very small financial transaction, typically under $1, enabled by low-fee blockchain networks for pay-per-call API pricing.

Multi-Agent System

An architecture where multiple AI agents collaborate, each with its own role, tools, and wallet, to accomplish complex tasks.

O

On-Chain Settlement

The process of recording and finalizing a payment transaction on a blockchain, providing immutable proof of payment.

P

Pay-Per-Call

A pricing model where each individual API call is billed as a separate micro-transaction, rather than through subscriptions or rate-limited tiers.

S

SKILL.md

A markdown file that teaches AI agents how to interact with an API — including authentication, endpoints, and payment handling.

Spending Limits

Configurable caps on how much an AI agent can spend per transaction, per day, or per billing cycle.

Stablecoin

A cryptocurrency designed to maintain a stable value relative to a reference asset, typically the US dollar.

U

USDC

A US dollar-pegged stablecoin issued by Circle, used as the payment currency for all Mithril transactions.

W

Web Scraping

The automated extraction of data from websites, commonly used by AI agents to gather information from the open web.

X

x402 Protocol

An open payment protocol that uses HTTP 402 Payment Required to enable pay-per-call API transactions for AI agents.

22 terms