How do I install the Authoring Specs skill?

Run npx skillmds@latest add x402-foundation/authoring-specs in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

What does the Authoring Specs skill do?

Guidelines for authoring x402 specification files. Use when writing or proposing a new x402 spec, such as a per-network scheme spec (scheme_ _ .md). It is listed under Coding & Dev Tools on SkillMD.

Is Authoring Specs safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Authoring Specs?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Authoring Specs free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Authoring Specs?

x402-foundation (@x402-foundation) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Authoring Specs by x402-foundation — Agent Skill

Name: Authoring Specs
Author: x402-foundation

File contents

Authoring x402 specs

Guidance for writing x402 specification files under specs/. Use RFC-2119 keywords for normative statements (MUST / MUST NOT, SHOULD / SHOULD NOT, MAY).

General rules

These apply to every spec type (scheme, extension). The references below add type-specific detail.

Naming

Name schemes and extensions in lowercase, hyphen-separated kebab-case (e.g. batch-settlement, offer-receipt), never camelCase.

Protocol version, networks, and units

Target protocol v2 only: x402Version: 2, the amount field (not v1's maxAmount), and the PAYMENT-REQUIRED / PAYMENT-SIGNATURE / PAYMENT-RESPONSE headers (not v1's X-PAYMENT / X-PAYMENT-RESPONSE). See the v1 to v2 migration guide.
Use canonical CAIP-2 network notation (e.g. eip155:84532, not base-sepolia).
Use atomic units for all amounts.

Wire format

Be transport agnostic: specify message contents, not how a particular transport carries them.
Reference core types (PaymentRequirements, PaymentPayload, SettlementResponse) from x402-specification-v2.md.
Every field a spec defines on the wire must be consumed by a downstream role. Do not include human-readable or otherwise purely informational fields.
Reuse field names, patterns, and conventions established by existing specs instead of coining new ones.

References

New network scheme spec (scheme_<name>_<chain>.md): see references/new-network-scheme-spec.md.
New extension spec: to be added.

Frequently asked questions

Authoring Specs