Linq

Linq is an API-first messaging platform that lets you reach people on iMessage, SMS, and RCS through real conversations. Linq handles the messaging plumbing — Apple and carrier delivery, group chats, read receipts, typing indicators, reactions, and attachments — behind a single REST API designed for programmatic access.

Why Linq?

• iMessage, SMS, and RCS in one API: Send and receive across all three channels from the same chats and phone numbers, with automatic delivery over the best available service.
• Rich conversations: Media, link previews, screen and bubble effects, tapback reactions, inline replies, voice memos, and editable messages — not just plain text.
• Group chat management: Create groups, add and remove participants, rename chats, update icons, and leave conversations.
• Capability checks: Verify whether an address supports iMessage or RCS before you send, so you pick the right channel every time.
• Real-time webhooks: Subscribe to message, reaction, participant, and call events with HMAC-SHA256 signature verification.

Using Linq in Sim

Sim's Linq integration connects your agentic workflows directly to Linq using an API key. With 34 operations spanning chats, messages, attachments, phone numbers, capability checks, contact cards, and webhook subscriptions, you can build conversational messaging automations without writing backend code.

Key benefits of using Linq in Sim:

• Conversational agents: Send and read messages in iMessage, SMS, or RCS chats, react with tapbacks, and reply inline to build natural two-way conversations.
• Reliable delivery: Check iMessage/RCS capability and set a preferred service so each message goes out over the right channel.
• Files and voice: Upload attachments up to 100MB and send media or voice memos straight from your workflow.
• Event-driven flows: Manage webhook subscriptions so workflows can react to inbound messages, reactions, and participant changes.

Usage Instructions

Reach people on iMessage, SMS, and RCS through Linq. Start chats, send messages with media, links, effects, and replies, send voice memos, react with tapbacks, manage group participants, check iMessage/RCS capability, configure contact cards, and subscribe to webhook events — all through a single Linq API key.

Tools

linq_add_participant

Add a participant to a group chat (3+ existing participants)

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Output

linq_check_imessage

Check whether an address (phone number or email) supports iMessage

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Output

linq_check_rcs

Check whether an address (phone number or email) supports RCS

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Output

linq_create_attachment

Upload a file to Linq as a reusable attachment (max 100MB) and get an attachment ID to send in messages

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Output

linq_create_chat

Start a new iMessage, SMS, or RCS chat and send the first message

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Output

linq_create_contact_card

Set up a contact card (Name and Photo Sharing) for a phone number

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linq_create_webhook_subscription

Subscribe an HTTPS endpoint to Linq webhook events

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linq_delete_attachment

Permanently delete an attachment owned by your account

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linq_delete_message

Delete a message from the Linq API only (does not unsend it; recipients still see it)

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linq_delete_webhook_subscription

Delete a webhook subscription from your account

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linq_edit_message

Edit the text of a sent message (up to 5 times, within 15 minutes of sending; iMessage only)

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linq_get_attachment

Retrieve metadata for an attachment, including its download URL and status

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linq_get_chat

Retrieve a chat by ID, including participants and line health

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linq_get_contact_card

Retrieve contact cards, optionally filtered by phone number

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linq_get_message

Retrieve a single message by ID, including parts, reactions, and delivery status

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linq_get_webhook_subscription

Retrieve a webhook subscription by ID

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linq_leave_chat

Leave an iMessage group chat (4+ active participants; not supported for direct chats)

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linq_list_chats

List chats, optionally filtered by sender or participant handle

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linq_list_messages

List messages in a chat with pagination

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linq_list_phone_numbers

List all phone numbers assigned to your partner account, with line health

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linq_list_thread

List all messages in the thread that contains a given message

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linq_list_webhook_events

List all webhook event types available to subscribe to

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linq_list_webhook_subscriptions

List all webhook subscriptions on your account

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linq_mark_chat_read

Mark all messages in a chat as read

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linq_react_to_message

Add or remove a tapback reaction on a message

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linq_remove_participant

Remove a participant from a group chat (minimum 3 participants must remain)

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linq_send_message

Send a message to an existing chat, with optional media, link, effect, or reply

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linq_send_voice_memo

Send a voice memo to a chat from a URL or a pre-uploaded attachment

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linq_share_contact_card

Share your configured contact card (Name and Photo Sharing) with a chat

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linq_start_typing

Show a typing indicator in a one-on-one chat (iMessage only, not group chats)

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linq_stop_typing

Stop the typing indicator in a one-on-one chat (iMessage only, not group chats)

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linq_update_chat

Update chat properties such as group display name and icon

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linq_update_contact_card

Partially update an existing active contact card for a phone number

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linq_update_webhook_subscription

Update a webhook subscription (target URL, events, phone filter, or active state)

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