Email skills for agents
Three open-source Agent Skills that teach your coding agent to send, receive and safely act on email with mails.ai.
Setup
Add them in seconds
One command adds the skills to your project. It finds all three and asks which to add; --skill picks one, -a the agent and -g installs them for your user.
npx skills add mailsai/skillsIn action
See the skills in action
Claude Code, with the skills added, checks a message before it answers it.
What’s inside
Three skills,
two tools
Each skill is a folder: a SKILL.md, reference notes and runnable examples.
mails
What an agent needs to use its own address: sending, receiving, threads, drafts and webhooks, by API, SDK or MCP.
agent-inbox
For an agent that acts on the mail it reads: five levels of protection, and webhook signature checks.
email-best-practices
Custom sending domains, bounces, complaints and unsubscribes, and what mails.ai refuses and the law requires.
CLI
The mails command line: send and receive email, follow events live, and add the MCP server to your AI client.
MCP server
The hosted server gives any MCP client the email tools. The skills package registers it as an Agent Plugin.
Frequently asked questions
What are Agent Skills?
Which agents can use them?
How do I install only one skill?
Can I install them without the skills command?
Do I still need the MCP server?
Does the plugin hold my API key?
Can I try the examples without sending real mail?
What does agent-inbox protect against?
Are the skills open source?
“Replies come back as events with an injection score already on them. We deleted a whole layer of parsing code the week we switched, and we gate on the quarantine flag, so our agent never sees the ones that look like attacks.”
“Moving our agent onto our own domain was a few DNS records at the registrar. No nameserver move, and our existing mail kept working. Replies to the agent still come back to its inbox, threaded with the message they answer.”
“The 422 on cold outreach is the feature I didn’t know I wanted. An agent can’t talk itself into emailing strangers.”
“Our tests send to the test address and wait for the real reply, so the whole loop is covered before a customer ever writes in. It answers in about a second, which keeps the suite fast.”
“Adding the MCP server was one JSON block. Claude Code could send and read its own inbox a minute later.”
“A reputation score per agent tells us exactly which one needs attention, instead of one number for the whole account. It comes from each agent’s own replies, bounces and complaints, and we read it from the API.”
“Sends and replies have separate allowances, so a busy inbox never eats our sending quota. Pricing was the easy part.”
“Half our agents are LangGraph in Python and half are Node. Both SDKs make the same calls, so the team doesn’t have to think about it.”
“Signed webhooks, retries with backoff and an event id to dedupe on. The boring plumbing, done properly.”
“We signed up, made a key and sent our first message without talking to anyone, and the free tier never asked for a card. That’s how infrastructure should feel.”
Give your first agent an inbox
Free covers 3,000 emails and 3,000 inbound replies a month, with no card. Upgrade when your agents get busy.
Get your API key