Agent skill

Email System

by gjovanovicst in gjovanovicst/golang-auth-api

Complete documentation of the email subsystem including template resolution, variable pipeline, rendering engines, SMTP config, and default templates.

MITAuto-check passedBackend & APIs

Install Email System

skills CLI

$ npx skills add gjovanovicst/golang-auth-api --skill email-system -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install gjovanovicst/golang-auth-api email-system --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/gjovanovicst/golang-auth-api.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.opencode/skills/email-system .claude/skills/email-system && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "email-system" agent skill from https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system into .claude/skills/email-system/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "email-system", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add gjovanovicst/golang-auth-api --skill email-system -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install gjovanovicst/golang-auth-api email-system --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/gjovanovicst/golang-auth-api.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.opencode/skills/email-system .agents/skills/email-system && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "email-system" agent skill from https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system into .agents/skills/email-system/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "email-system", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add gjovanovicst/golang-auth-api --skill email-system -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install gjovanovicst/golang-auth-api email-system --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/gjovanovicst/golang-auth-api.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.opencode/skills/email-system .cursor/skills/email-system && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "email-system" agent skill from https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system into .cursor/skills/email-system/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "email-system", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/gjovanovicst/golang-auth-api.git --path .opencode/skills/email-system

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add gjovanovicst/golang-auth-api --skill email-system -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install gjovanovicst/golang-auth-api email-system --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/gjovanovicst/golang-auth-api.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.opencode/skills/email-system .gemini/skills/email-system && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "email-system" agent skill from https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system into .gemini/skills/email-system/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "email-system", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install gjovanovicst/golang-auth-api email-system

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add gjovanovicst/golang-auth-api --skill email-system -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/gjovanovicst/golang-auth-api.git skills-src && mkdir -p .github/skills && cp -r skills-src/.opencode/skills/email-system .github/skills/email-system && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "email-system" agent skill from https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system into .github/skills/email-system/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "email-system", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add gjovanovicst/golang-auth-api --skill email-system -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install gjovanovicst/golang-auth-api email-system --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/gjovanovicst/golang-auth-api.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.opencode/skills/email-system .opencode/skills/email-system && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "email-system" agent skill from https://github.com/gjovanovicst/golang-auth-api/tree/main/.opencode/skills/email-system into .opencode/skills/email-system/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "email-system", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: email-system
GitHub stars: 130
Token cost: ~1.7k tokens
SKILL.md length: 473 words
Files: 1
Skills in repo: 6
Repo updated: Jul 30, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Complete documentation of the email subsystem including template resolution, variable pipeline, rendering engines, SMTP config, and default templates.

Tasks that involve Transactional email
SKILL.md covers Architecture, Send Pipeline, Template Resolution Chain and SMTP Resolution Chain, plus 8 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
Tasks that involve Authentication

What it does

Email System is an agent skill from gjovanovicst/golang-auth-api. Complete documentation of the email subsystem including template resolution, variable pipeline, rendering engines, SMTP config, and default templates.

Its SKILL.md is about 1.7k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Backend & APIs, covering Transactional email and Authentication. The repository describes itself as: A modern, production-ready Go REST API for authentication and authorization, featuring social login, email verification, JWT, and Redis integration. The licence is MIT.

When your agent uses it

Tasks that involve Transactional email
Tasks that involve Authentication

Example prompts

“/email-system”

What it can do on your machine

Read from SKILL.md and the folder at commit 795d18d. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Email System loads about 1.7k tokens when it runs. Until then it costs about 41 tokens; SKILL.md has 473 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~41
When it runs · the whole SKILL.md, loaded when a task matches: ~1.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from gjovanovicst/golang-auth-api at commit 795d18d, republished under its MIT licence (© gjovanovicst). 473 words, ~1,722 tokens.

Download SKILL.mdSave it as .claude/skills/email-system/SKILL.md (or your agent's skills folder).

name: email-system
description: Complete documentation of the email subsystem including template resolution, variable pipeline, rendering engines, SMTP config, and default templates.
license: MIT

Architecture

The email system is in internal/email/ and follows a multi-layered pipeline:

Service (orchestrator)
  |-- VariableResolver  -> resolves template variables from 4 sources
  |-- Renderer          -> renders templates with 3 supported engines
  |-- Sender            -> sends via SMTP (or logs in dev mode)
  |-- Repository        -> DB access for types, templates, server configs

Entry point: email.Service.SendEmailWithContext(appID, emailTypeCode, toEmail, userID, vars)

Send Pipeline

1. VariableResolver.ResolveVariables()  -- build final variable map
2. resolveTemplate()                     -- find the right template
3. Renderer.RenderTemplate()             -- render subject, HTML, text
4. resolveSMTPConfigForTemplate()        -- find the right SMTP config
5. Sender.Send()                         -- deliver via SMTP

Template Resolution Chain

Defined in internal/email/service.go method resolveTemplate:

1. DB: app-specific template
   WHERE app_id = ? AND email_type_id = ? AND is_active = true

2. DB: global default template
   WHERE app_id IS NULL AND email_type_id = ? AND is_active = true

3. Hardcoded fallback
   defaults.go -> GetDefaultTemplate(typeCode)

SMTP Resolution Chain

Defined in internal/email/service.go method resolveSMTPConfig:

1. DB: per-app config
   WHERE app_id = ? AND is_active = true AND is_default = true

2. DB: global config
   WHERE app_id IS NULL AND is_active = true AND is_default = true

3. Empty config -> dev/fallback mode (log to stdout)

With template override (resolveSMTPConfigForTemplate):

1. If template has ServerConfigID -> use that specific config by ID
2. Otherwise -> standard chain above
3. Apply template-level FromEmail/FromName overrides on top

Variable Resolution Pipeline

Defined in internal/email/resolver.go. Resolution priority (lowest to highest):

Layer	Source	Method	Example Variables
1 (lowest)	Static defaults	`applyStaticDefaults`	DefaultValue from email_types.variables JSONB
2	App/system settings	`applySettingsVars`	`app_name`, `frontend_url`
3	User profile	`applyUserVars`	`user_email`, `user_name`, `first_name`, `last_name`, `locale`, `profile_picture`
Always	Fallback	--	`user_email` = toEmail if not set
4 (highest)	Explicit caller vars	direct map copy	`verification_link`, `code`, `reset_link`, etc.

Variable Sources

Source	Variables	How Resolved
`user` (auto)	`user_email`, `user_name`, `first_name`, `last_name`, `locale`, `profile_picture`	From DB user record
`setting` (auto)	`app_name`, `frontend_url`	app name from DB/env, frontend_url from env
`explicit` (caller)	`verification_link`, `verification_token`, `reset_link`, `code`, `expiration_minutes`, `change_time`, `magic_link`	Must be passed by calling code

All variable constants are in internal/email/types.go.

Template Engines

Defined in internal/email/renderer.go:

Engine	Constant	Syntax	HTML Escaping
Go Template	`go_template`	`{{.AppName}}` or `{{.app_name}}`	Yes (automatic)
Placeholder	`placeholder`	`{app_name}`	No
Raw HTML	`raw_html`	`{{.AppName}}`	No (unsafe)

The renderer converts all variables to both snake_case and PascalCase forms, so templates can use either style.

Subject lines always use Go template syntax regardless of engine.

Email Types (7 built-in)

Constants in internal/email/types.go:

Code	Constant	Variables Used
`email_verification`	TypeEmailVerification	app_name, verification_link, user_email
`password_reset`	TypePasswordReset	app_name, reset_link, expiration_minutes
`two_fa_code`	TypeTwoFACode	app_name, code, expiration_minutes
`welcome`	TypeWelcome	app_name, user_email
`account_deactivated`	TypeAccountDeactivated	app_name, user_email
`password_changed`	TypePasswordChanged	app_name, change_time, user_email
`magic_link`	TypeMagicLink	app_name, magic_link, expiration_minutes

Default Templates

Defined in internal/email/defaults.go. All use go_template engine, provide both HTML and plain text bodies, and use responsive table-based layout with consistent styling (indigo #4f46e5 primary color, 600px max width).

Service Methods

Show full SKILL.md (190 more words)Show less

Typed Send Methods (in `internal/email/service.go`)

Method	Email Type	Extra Vars
`SendVerificationEmail`	email_verification	verification_link (built from FRONTEND_URL + token)
`SendPasswordResetEmail`	password_reset	reset_link, expiration_minutes=60
`Send2FACodeEmail`	two_fa_code	code, expiration_minutes=5
`SendWelcomeEmail`	welcome	(none)
`SendAccountDeactivatedEmail`	account_deactivated	(none)
`SendPasswordChangedEmail`	password_changed	change_time
`SendMagicLinkEmail`	magic_link	magic_link, expiration_minutes=10
`SendAdmin2FACodeEmail`	N/A (hardcoded HTML)	Bypasses app-scoped resolution
`SendAdminMagicLinkEmail`	N/A (hardcoded HTML)	Bypasses app-scoped resolution

Management Methods

Template CRUD: GetTemplatesByApp, GetGlobalDefaultTemplates, GetTemplateByID, SaveAppTemplate, SaveGlobalTemplate, DeleteTemplate, ResetTemplateToDefault, PreviewTemplate

Email type CRUD: GetAllEmailTypes, GetEmailTypeByCode, CreateEmailType, UpdateEmailType, DeleteEmailType

Server config CRUD: GetServerConfig, SaveServerConfig, DeleteServerConfig, GetAllServerConfigs, etc.

SMTP Sending (`internal/email/sender.go`)

Uses gopkg.in/mail.v2.

Dev mode: If SMTP host is empty or "smtp.example.com", logs email to stdout (no error).

TLS handling:

Port 465: implicit SSL (d.SSL = true)
Other ports: MandatoryStartTLS, MinVersion TLS 1.2

Error behavior:

Send(): on SMTP failure, logs email as fallback and returns nil (email failure doesn't break business flow)
SendTest(): always returns errors (for admin testing)

Database Models

EmailType (pkg/models/email_type.go) -- types with variable definitions as JSONB
EmailTemplate (pkg/models/email_template.go) -- templates scoped to app or global
EmailServerConfig (pkg/models/email_server_config.go) -- SMTP configs scoped to app or global

When To Use This Skill

Load this skill when working on email sending, email templates, SMTP configuration, template variables, or any email-related feature.

Files

Just SKILL.md in .opencode/skills/email-system of gjovanovicst/golang-auth-api.

Open the folder on GitHubat commit 795d18d

Compare with similar skills

Email System next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Email System compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Email System this skillgjovanovicst/golang-auth-api	130	—	~1.7k	Automated safety check: Pass	MIT	2 mo ago
Reading Mailcatcher APIbitwarden/ai-plugins	155	—	~2.3k	Automated safety check: Pass	Custom licence	yesterday
Configuration Messaginggreenpau/caddy-security	2.3k	—	~1.6k	Automated safety check: Pass	Apache-2.0	5 days ago
ResendLeoYeAI/openclaw-master-skills	2.2k	—	~5.1k	Automated safety check: Pass	MIT	2 mo ago
Fortify Developmentcoollabsio/coolify	63k	4 repos	~1.9k	Automated safety check: Pass	MIT	yesterday
Supabase Development and Debuggingsupabase/agent-skills	2.7k	3 repos	~3.6k	Automated safety check: Pass	MIT	8 days ago

Similar skills

Reading Mailcatcher API
bitwarden/ai-plugins
Official
Retrieves a link from Mailcatcher. An agent skill from bitwarden/ai-plugins.
155 GitHub stars~2.3k tokensUpdated yesterday
Backend & APIsAuto-check passed
Configuration Messaging
greenpau/caddy-security
Configure email and file messaging providers, SMTP transport, sender/authentication, templates, and registration delivery wiring.
2.3k GitHub stars~1.6k tokensUpdated 5 days ago
Backend & APIsAuto-check passed
Resend
LeoYeAI/openclaw-master-skills
Resend API integration with managed authentication. An agent skill from LeoYeAI/openclaw-master-skills.
2.2k GitHub stars~5.1k tokensUpdated 2 mo ago
Backend & APIsAuto-check passed
Fortify Development
coollabsio/coolify
ACTIVATE when the user works on authentication in Laravel. An agent skill from coollabsio/coolify.
63k GitHub starsUsed in 4 repos~1.9k tokens
Backend & APIsAuto-check passed
Supabase Development and Debugging
supabase/agent-skills
Official
General Supabase skill for database, auth, Edge Functions, Realtime and storage work, plus client libraries, migrations, security audits, debugging and reading logs.
2.7k GitHub starsUsed in 3 repos~3.6k tokens
Backend & APIsAuto-check passed
Better Auth Best Practices
latitude-dev/latitude-llm
Configure Better Auth server and client, set up database adapters, manage sessions, add plugins, and handle environment variables.
4.7k GitHub starsUsed in 7 repos~1.6k tokens
Backend & APIsAuto-check passed

Questions about Email System

What does Email System do?

Complete documentation of the email subsystem including template resolution, variable pipeline, rendering engines, SMTP config, and default templates. Email System is an agent skill from gjovanovicst/golang-auth-api. Complete documentation of the email subsystem including template resolution, variable pipeline, rendering engines, SMTP config, and default templates.

When should I use Email System?

Email System fits situations like: tasks that involve Transactional email; tasks that involve Authentication.

How do I install Email System in Claude Code?

Run `npx skills add gjovanovicst/golang-auth-api --skill email-system -a claude-code`. Or copy the skill folder (.opencode/skills/email-system in gjovanovicst/golang-auth-api) into .claude/skills/email-system in your project. Claude Code loads it when a task matches its description.

How do I install Email System in Codex?

Run `npx skills add gjovanovicst/golang-auth-api --skill email-system -a codex`. Or copy the skill folder (.opencode/skills/email-system in gjovanovicst/golang-auth-api) into .agents/skills/email-system in your project. Codex loads it when a task matches its description.

Can I use Email System in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add gjovanovicst/golang-auth-api --skill email-system -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/email-system, .gemini/skills/email-system, .github/skills/email-system and .opencode/skills/email-system in your project.

What does Email System need to run?

SKILL.md names no scripts, command-line tools or credentials: Email System is instructions for the agent only.

Does Email System access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Email System safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Email System use?

Email System is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Email System use?

About 1.7k tokens (SKILL.md is roughly 6.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Email System?

Skills that share tags, products or a category with Email System: Reading Mailcatcher API (bitwarden/ai-plugins, 155 stars), Configuration Messaging (greenpau/caddy-security, 2.3k stars), Resend (LeoYeAI/openclaw-master-skills, 2.2k stars) and Fortify Development (coollabsio/coolify, 63k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Email System?

gjovanovicst (a GitHub user) maintains it in gjovanovicst/golang-auth-api, which has 130 GitHub stars. The repository holds 6 skills in this directory. The repository was last updated on July 30, 2026.

Source: gjovanovicst/golang-auth-api on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Email System

Facts

At a glance

What it does

When your agent uses it

Example prompts

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Architecture

Send Pipeline

Template Resolution Chain

SMTP Resolution Chain

Variable Resolution Pipeline

Variable Sources

Template Engines

Email Types (7 built-in)

Default Templates

Service Methods

Typed Send Methods (in internal/email/service.go)

Management Methods

SMTP Sending (internal/email/sender.go)

Database Models

When To Use This Skill

Files

Compare with similar skills

Similar skills

More from gjovanovicst/golang-auth-api

Related

Questions about Email System

Typed Send Methods (in `internal/email/service.go`)

SMTP Sending (`internal/email/sender.go`)