diff --git a/README.md b/README.md
index 2be8385..4ba398a 100644
--- a/README.md
+++ b/README.md
@@ -134,7 +134,7 @@ const { accountId, conversationId } = adapter.decodeThreadId(threadId);
 | Edit messages | Partial | Telegram only |
 | Delete messages | Partial | Telegram, X (full delete); Bluesky, Reddit (self-only) |
 | Reactions | Partial | Telegram and WhatsApp (add/remove emoji) |
-| Typing indicators | Partial | Facebook Messenger and Telegram |
+| Typing indicators | Partial | Facebook Messenger, Telegram, and WhatsApp (requires recent inbound message) |
 | AI streaming | Partial | Post+edit on Telegram; single post on others |
 | File attachments | Yes | Via media upload endpoint |
 | Fetch messages | Yes | Full conversation history |
@@ -148,7 +148,7 @@ const { accountId, conversationId } = adapter.decodeThreadId(threadId);
 |---------|----|----|----------|----------|---|---------|--------|
 | Send text | Y | Y | Y | Y | Y | Y | Y |
 | Buttons | Y | Y | Y | Y | - | - | - |
-| Typing | Y | - | Y | - | - | - | - |
+| Typing | Y | - | Y | Y | - | - | - |
 | Delete | - | - | Y | - | Y | Self | Self |
 | Reactions | - | - | Y | Y | - | - | - |
 | Media | Y | Y | Y | Y | Y | - | - |
diff --git a/src/api-client.ts b/src/api-client.ts
index d9b9402..ec22856 100644
--- a/src/api-client.ts
+++ b/src/api-client.ts
@@ -131,7 +131,9 @@ export class ZernioApiClient {
    * Send a typing indicator for a conversation.
    * POST /v1/inbox/conversations/{conversationId}/typing
    *
-   * Supported on Facebook Messenger and Telegram. No-op on other platforms.
+   * Supported on Facebook Messenger, Telegram, and WhatsApp. No-op on
+   * other platforms. WhatsApp additionally requires a recent inbound
+   * message in the conversation (Meta references the inbound message id).
    */
   async sendTyping(conversationId: string, accountId: string): Promise<void> {
     await this.request<{ success: boolean }>(