Agent Skills: Gmail API

Gmail API

Read, send, and manage emails via Google's Gmail REST API.

Official docs: https://developers.google.com/workspace/gmail/api/reference/rest

When to Use

Use this skill when you need to:

• Read and search emails
• Send emails or reply to threads
• Manage drafts
• Create and manage labels
• List and modify threads
• Get user profile information

Prerequisites

1. Create Google Cloud Project

1. Go to https://console.cloud.google.com
2. Create a new project or select existing
3. Enable Gmail API: https://console.cloud.google.com/apis/library/gmail.googleapis.com

2. Configure OAuth Consent Screen

1. Go to https://console.cloud.google.com/apis/credentials/consent
2. Select External → Create
3. Fill required fields (app name, support email, developer email)
4. Click Save and Continue through Scopes (skip adding scopes)
5. In Audience section, click Add Users and add your Gmail address as test user
6. Save and continue to finish

3. Create OAuth Client ID

1. Go to https://console.cloud.google.com/apis/credentials
2. Click Create Credentials → OAuth client ID
3. Choose Web application (not Desktop)
4. Add Authorized redirect URI: https://developers.google.com/oauthplayground
5. Click Create and note the Client ID and Client Secret

4. Get Refresh Token (OAuth Playground)

1. Go to https://developers.google.com/oauthplayground/
2. Click Settings (gear icon ⚙️) → Check Use your own OAuth credentials
3. Enter your Client ID and Client Secret
4. In the left panel, enter scope: https://www.googleapis.com/auth/gmail.modify
5. Click Authorize APIs → Sign in with your test user account
6. Click Exchange authorization code for tokens
7. Copy the Refresh token

5. Set Environment Variables

export GMAIL_CLIENT_ID="your-client-id"
export GMAIL_CLIENT_SECRET="your-client-secret"
export GMAIL_REFRESH_TOKEN="your-refresh-token"

Get Access Token

Access tokens expire after 1 hour. Use refresh token to get a new one and save to /tmp:

bash -c 'curl -s -X POST "https://oauth2.googleapis.com/token" -d "client_id=$GMAIL_CLIENT_ID" -d "client_secret=$GMAIL_CLIENT_SECRET" -d "refresh_token=$GMAIL_REFRESH_TOKEN" -d "grant_type=refresh_token"' | jq -r '.access_token' > /tmp/gmail_token.txt

# Verify token was obtained
head -c 20 /tmp/gmail_token.txt && echo "..."

Important: When using $VAR in a command that pipes to another command, wrap the command containing $VAR in bash -c '...'. Due to a Claude Code bug, environment variables are silently cleared when pipes are used directly.

Placeholders: Values in {curly-braces} like {message-id} are placeholders. Replace them with actual values when executing.

User Profile

Get Profile

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/profile" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Messages

List Messages

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/messages?maxResults=10" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

List Messages with Query

Search using Gmail query syntax:

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/messages?q=is:unread&maxResults=10" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Common queries:

• is:unread - Unread messages
• from:example@gmail.com - From specific sender
• subject:hello - Subject contains "hello"
• after:2024/01/01 - After date
• has:attachment - Has attachments
• label:INBOX - In inbox

Get Message

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Get Message (Metadata Only)

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}?format=metadata&metadataHeaders=From&metadataHeaders=Subject&metadataHeaders=Date" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Send Email

# Create RFC 2822 message and base64url encode
RAW_MESSAGE=$(echo -e "To: {recipient-email}\r\nSubject: {subject}\r\nContent-Type: text/plain; charset=utf-8\r\n\r\n{body-text}" | base64 | tr '+/' '-_' | tr -d '=')

Write to /tmp/gmail_request.json:

{
  "raw": "$RAW_MESSAGE"
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/messages/send" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Reply to Thread

# Include In-Reply-To and References headers for proper threading
RAW_MESSAGE=$(echo -e "To: {recipient-email}\r\nSubject: Re: {original-subject}\r\nIn-Reply-To: <{original-message-id}>\r\nReferences: <{original-message-id}>\r\nContent-Type: text/plain; charset=utf-8\r\n\r\n{reply-text}" | base64 | tr '+/' '-_' | tr -d '=')

Write to /tmp/gmail_request.json:

{
  "raw": "$RAW_MESSAGE",
  "threadId": "{thread-id}"
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/messages/send" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Modify Message Labels

Write to /tmp/gmail_request.json:

{
  "addLabelIds": ["STARRED"],
  "removeLabelIds": ["UNREAD"]
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}/modify" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Trash Message

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}/trash" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Delete Message Permanently

bash -c 'curl -s -X DELETE "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Threads

List Threads

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/threads?maxResults=10" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Get Thread

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/threads/{thread-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Trash Thread

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/threads/{thread-id}/trash" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Labels

List Labels

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/labels" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"' | jq '.labels[] | {id, name, type}'

Create Label

Write to /tmp/gmail_request.json:

{
  "name": "{label-name}",
  "labelListVisibility": "labelShow",
  "messageListVisibility": "show"
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/labels" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Delete Label

bash -c 'curl -s -X DELETE "https://gmail.googleapis.com/gmail/v1/users/me/labels/{label-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Drafts

List Drafts

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/drafts" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Create Draft

RAW_MESSAGE=$(echo -e "To: {recipient-email}\r\nSubject: {subject}\r\nContent-Type: text/plain; charset=utf-8\r\n\r\n{body-text}" | base64 | tr '+/' '-_' | tr -d '=')

Write to /tmp/gmail_request.json:

{
  "message": {
    "raw": "$RAW_MESSAGE"
  }
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/drafts" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Send Draft

Write to /tmp/gmail_request.json:

{
  "id": "{draft-id}"
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/drafts/send" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Delete Draft

bash -c 'curl -s -X DELETE "https://gmail.googleapis.com/gmail/v1/users/me/drafts/{draft-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Attachments

Get Attachment

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}/attachments/{attachment-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"' | jq -r '.data' | base64 -d > attachment.bin

Settings

Get Vacation Settings

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/settings/vacation" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Update Vacation Settings

Write to /tmp/gmail_request.json:

{
  "enableAutoReply": true,
  "responseSubject": "Out of Office",
  "responseBodyPlainText": "I am currently out of office.",
  "restrictToContacts": false,
  "restrictToDomain": false
}

Then run:

bash -c 'curl -s -X PUT "https://gmail.googleapis.com/gmail/v1/users/me/settings/vacation" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

List Filters

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/settings/filters" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"'

Create Filter

Write to /tmp/gmail_request.json:

{
  "criteria": {
    "from": "{filter-email}"
  },
  "action": {
    "addLabelIds": ["TRASH"],
    "removeLabelIds": ["INBOX"]
  }
}

Then run:

bash -c 'curl -s -X POST "https://gmail.googleapis.com/gmail/v1/users/me/settings/filters" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)" --header "Content-Type: application/json" -d @/tmp/gmail_request.json'

Common Scopes

| Scope | Permission | |-------|------------| | gmail.readonly | Read-only access | | gmail.send | Send emails only | | gmail.compose | Create drafts and send | | gmail.modify | Read, send, delete, manage | | gmail.labels | Manage labels only | | gmail.settings.basic | Manage basic settings | | gmail.settings.sharing | Manage sensitive settings |

Use full URL: https://www.googleapis.com/auth/gmail.modify

Decode Message Body

Gmail returns message body as base64url encoded. To decode:

bash -c 'curl -s "https://gmail.googleapis.com/gmail/v1/users/me/messages/{message-id}" --header "Authorization: Bearer $(cat /tmp/gmail_token.txt)"' | jq -r '.payload.body.data // .payload.parts[0].body.data' | tr '_-' '/+' | base64 -d

Guidelines

1. Token Refresh: Access tokens expire in 1 hour; always refresh before API calls
2. Rate Limits: Gmail API has quota limits; implement exponential backoff
3. Batch Requests: Use batch endpoints for multiple operations
4. Message Format: Messages must be RFC 2822 compliant and base64url encoded
5. Scopes: Request minimum required scopes for your use case

API Reference

• REST Reference: https://developers.google.com/workspace/gmail/api/reference/rest
• Guides: https://developers.google.com/workspace/gmail/api/guides
• OAuth Playground: https://developers.google.com/oauthplayground/
• Scopes: https://developers.google.com/identity/protocols/oauth2/scopes#gmail