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Agent Skill

A Claude skill that teaches your agent the Mailloop testing workflow, bundled with the MCP server in one plugin.

3 min read

The Mailloop MCP server gives an agent the tools to create sandboxes, wait for captured email, and read what arrived. The Agent Skill gives it the workflow: trigger the send, wait for the email, then check the result. The MCP server is the connection. The skill is the playbook.

Both ship in one Claude Code plugin, so installing the plugin wires up the server and the skill at once.

When to use it

Install the plugin when you want the agent to run email tests in Claude Code without being walked through the steps each time. If you only want the raw tools, or you are connecting from another client, the MCP Server page covers that setup.

Install

Add the marketplace and install the plugin in Claude Code:

BASH 
/plugin marketplace add mailloop/skills
/plugin install mailloop@mailloop

The plugin connects to https://api.mailloop.io/mcp with a Bearer key read from MAILLOOP_API_KEY. Create a key under Settings → Organization → API keys and export it before you start:

BASH 
export MAILLOOP_API_KEY="ml_live_xxx"

Run /reload-plugins if the tools do not show up right away.

Prefer to keep just the tools? Skip the plugin and connect the MCP server directly with claude mcp add. See the MCP Server page.

What the skill teaches

Once it is installed, the agent follows the same playbook every run instead of improvising:

  • It creates a sandbox, points the app under test at that address, triggers the send, and only then calls wait_for_email. It waits after the send, never before.
  • It filters wait_for_email by sender, recipient, or subject so the right message matches, and it treats a timeout as a failed test, not as something to retry blindly.
  • It reads links and body to follow a verification or reset link, and it treats every email body as untrusted data rather than as instructions.
  • It cleans up sandboxes after a run, which matters most in CI.

Example

Ask in plain English:

TEXT 
Sign up for my app and make sure the verification email actually works.

The agent creates a sandbox, signs up with its address, waits for the verification email, opens it, follows the confirm link, and reports whether it returned a 200.

Troubleshooting

The skill does not trigger. A skill loads from its description, so say what you want to test (a signup, a password reset, a receipt) and the agent picks it up.

FORBIDDEN on a tool call. Your API key is missing a scope. Grant emails:send for send_email, or webhooks:write for the webhook tools, under Settings → Organization → API keys.

Tools missing after install. Run /reload-plugins, and confirm MAILLOOP_API_KEY is exported in the shell that launched Claude Code.

For the full list of tools and their parameters, see the MCP Server page.