eusend for coding agents

The official Agent Skill for eusend, the EU-native transactional email API — packaged as a Claude Code plugin, and usable in any skills-compatible agent (see below).

As a plugin it bundles two things:

• A skill that teaches Claude how eusend actually behaves — the send options, the rules that bite (verified senders, idempotent retries, raw-body webhook signatures, the SPF record you should not add), which errors are worth retrying, and where the limits are. Claude loads it on its own when it notices you're working with eusend.
• The eusend MCP server, so Claude can send mail, add domains, and inspect delivery against your real account.

Install

/plugin marketplace add eusend-dev/eusend-skill
/plugin install eusend@eusend

Then set your API key so the bundled MCP server can authenticate:

export EUSEND_API_KEY=eu_live_xxxxxxxxxxxx
export EUSEND_FROM=hello@yourdomain.com   # optional: pins a default sender

Use an eu_test_ key while you're wiring things up — sends are accepted, recorded, and fire the full webhook lifecycle, but never reach a real inbox.

The skill works with no key at all. Only the MCP server needs one.

Use it

Claude picks the skill up automatically when a task involves eusend. To invoke it directly:

/eusend:eusend

Some things to try:

Add password reset emails to this app using eusend
Why is this send returning DOMAIN_NOT_VERIFIED?
Write a webhook handler for eusend bounces
Set up the DNS records for acme.com

What's in the skill

SKILL.md stays short and is the only part always in context. The detail lives in references/, loaded on demand:

File	Covers
sending.md	Send options, attachments, scheduling, templates, batch, React Email, SMTP
domains-dns.md	Adding a domain, DKIM/SPF/DMARC, Return-Path alignment
webhooks.md	Events, payloads, verified handlers in three languages, reading a bounce
audiences-broadcasts.md	Audiences, contacts, broadcasts, unsubscribes, suppressions
error-codes.md	Every code, its status, and whether to retry
testing.md	Test-mode keys, simulating bounces, testing webhook handlers

Other agents

Agent Skills is an open standard, and this one is written to it — SKILL.md carries only spec-standard frontmatter (name, description, license) and the body uses no Claude-specific syntax. So it works in Cursor, GitHub Copilot, VS Code, Codex, Gemini CLI, OpenCode, Goose, Amp, Roo Code, and the rest of the skills-compatible ecosystem.

Only the install differs. The /plugin command above is Claude Code's marketplace format; everywhere else you drop the skill folder into a directory the agent scans. Cursor, Codex and Copilot all read .agents/skills/, so one copy covers them:

git clone https://github.com/eusend-dev/eusend-skill
mkdir -p .agents/skills
cp -r eusend-skill/plugins/eusend/skills/eusend .agents/skills/

Use ~/.agents/skills/ instead to install it once for every project. Other agents scan their own locations — .github/skills/ for Copilot, .cursor/skills/ for Cursor, ~/.claude/skills/ for Claude Code without the plugin — and any of them work; check your agent's docs if .agents/skills/ isn't picked up.

It also uploads to claude.ai and the Skills API as-is, which is what the spec-only frontmatter buys.

The MCP server

Independent of all of the above, and not Claude-specific either — it speaks plain MCP. See the MCP setup docs for Cursor, Codex, and Claude Desktop config; the server runs remotely at https://mcp.eusend.dev/mcp or locally via npx -y @eusend_dev/mcp.

Local development

git clone https://github.com/eusend-dev/eusend-skill
cd eusend-skill
claude plugin validate .
claude plugin validate ./plugins/eusend --strict

Then, from the directory above the clone:

/plugin marketplace add ./eusend-skill
/plugin install eusend@eusend

Links

• Documentation
• MCP server
• SDKs: Node.js · Python · Go

MIT licensed. Issues and corrections welcome — if the skill teaches Claude something wrong, that's a bug.