> ## Documentation Index
> Fetch the complete documentation index at: https://sendmux.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Agent skills
> Install Sendmux Agent Skills so AI coding tools choose the right Sendmux API, CLI, MCP, or SDK workflow.
Sendmux Agent Skills teach AI coding tools how to send email, read mailboxes, manage team resources, and choose low-token Sendmux calls. Use them when your agent needs Sendmux context before it writes commands, API calls, or integration code.
Skills do not grant Sendmux access by themselves. Create API keys, authorise
MCP, or use agent access first, then let the skill choose the right surface
for the task. If you use agent access, immediately save the returned
`claim_token` and agent credential bundle before token exchange: mailbox
metadata, token endpoints, resource URLs, and `identity_assertion`. Keep the
`identity_assertion` or pre-claim token until the owner invite returns `202`.
## Install from a marketplace
Use the marketplace path when your AI tool supports plugins. It installs the full Sendmux pack and keeps marketplace updates separate from your project files.
1. Open **Customize**.
2. Go to **Plugins**.
3. In **Personal plugins**, click **+** and choose **Add marketplace**.
4. Choose **Add from a repository**.
5. Enter `Sendmux/skills`, then install the **Sendmux** plugin.
```text theme={null}
/plugin marketplace add Sendmux/skills
/plugin install sendmux@sendmux
/reload-plugins
```
Add the marketplace first.
```bash theme={null}
codex plugin marketplace add Sendmux/skills
```
Then open **Plugins** in the Codex app or `/plugins` in Codex CLI and install **Sendmux** from the Sendmux marketplace.
## Install with Agent Skills
Use `skills add` when your agent supports raw Agent Skills rather than plugin marketplaces.
```bash theme={null}
npx skills add Sendmux/skills
```
Install one skill when you only need a focused workflow.
```bash theme={null}
npx skills add Sendmux/skills --skill sendmux-send-email
```
Update installed skills later.
```bash theme={null}
npx skills update
```
## Supported targets
| Target | Recommended install |
| ---------------------------------- | ------------------------------------------------------------------------------------------------------- |
| Claude app, Claude Desktop, Cowork | Add marketplace from repository `Sendmux/skills`, then install **Sendmux**. |
| Claude Code | `/plugin marketplace add Sendmux/skills`, then `/plugin install sendmux@sendmux`. |
| Codex app and Codex CLI | `codex plugin marketplace add Sendmux/skills`, then install **Sendmux** from **Plugins** or `/plugins`. |
| Agent Skills clients | `npx skills add Sendmux/skills`. |
| Single-skill installs | `npx skills add Sendmux/skills --skill `. |
## What the pack teaches
| Skill | Use when |
| ------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| `sendmux-getting-started` | Choosing a Sendmux surface, setting up authentication, or making a first verified call. |
| `sendmux-send-email` | Sending one transactional email or batching multiple sends. |
| `sendmux-mailbox-agent` | Reading, triaging, replying from, or syncing one mailbox. |
| `sendmux-management` | Managing domains, mailboxes, sending accounts, webhooks, billing, and logs. |
| `sendmux-cli` | Running Sendmux commands from a terminal. |
| `sendmux-mcp-setup` | Connecting Sendmux MCP servers to an agent client. |
| `sendmux-token-efficient-usage` | Choosing low-token calls such as batch sends, counts, snippets, deltas, cursors, and conditional requests. |
| `sendmux-email-for-agents` | Giving an AI agent an inbox, a challenge-first self-registration flow, or a human-approved send workflow. |
## Choose the right surface
| Task | Default path |
| ---------------------------------------- | -------------------------------- |
| Agent already has Sendmux MCP connected | Use the relevant MCP tool first. |
| Terminal one-shot or scripted admin work | Use the `sendmux` CLI. |
| Application code | Use an SDK package. |
| Endpoint detail or uncommon operation | Use the API reference. |
Use send-capable `smx_mbx_` keys or owner-approved Sending-resource `smx_agent_` tokens for Sending work. Use `smx_mbx_` keys or scoped `smx_agent_` tokens for allowed Mailbox work. Use team-scoped `smx_root_` keys for Management work. Pre-claim `smx_agent_` tokens do not include `email.send`.
When an agent has no Sendmux credential, start with [agent access](/docs/guides/agent-access): request a registration challenge, solve it, register the mailbox at the `identity_endpoint` with `proof_of_work`, immediately save the returned `claim_token` and full agent credential bundle in a secure store such as 1Password, an OS keychain, or the agent platform's encrypted secret store before token exchange, exchange the identity assertion, then invite the human owner with the pre-claim access token. The claim token is required later for owner-approved sending and cannot create the owner invite. If the agent loses both the identity assertion and pre-claim token before the invite returns `202`, register again and invite immediately. If any agent-auth endpoint returns `429`, use `Retry-After` or `retry_after` before retrying.
## Next steps
Connect hosted or local Sendmux MCP tools.
Let an agent register a constrained mailbox and invite its owner.
Run Sendmux workflows from your terminal.
Choose an SDK package for application code.
Create scoped credentials for tools and agents.