MCP server
Connect Claude or ChatGPT to Gmail: the built-in route and the Kasar route
There are two ways to plug Claude into Gmail. Its Google connector, open to every user, searches, reads, drafts and sends from one Google account. The Kasar MCP server reads the same mailbox, but the assistant also sees the sender’s record, the open deal and your other conversations, and every send goes through a preview first. In ChatGPT, only a custom MCP app can write.
Facts checked on October 6, 2026
01Built-in route: Claude’s Gmail connector
According to Claude’s help centre, checked on 6 October 2026, the Google Workspace connectors (Gmail, Google Calendar, Google Drive) are available to every Claude and Claude Desktop user. On the Gmail side, Claude searches mail in plain language, reads it, writes drafts, sends, replies, forwards, and manages labels and threads. You switch it on from the + button in the chat, Connectors menu, once you have authorised your Google account.
The same page sets three limits. Claude reaches only the one Google account you connected. It reads attachment metadata, not attachment content. On Team and Enterprise plans, an organisation owner turns the connectors on before anyone can authenticate.
That connector works on the mailbox: it sees senders and threads. For a salesperson, the next question is nearly always “who is this person to us?”, and that answer lives in the CRM, not in Gmail.
What about ChatGPT?
OpenAI’s help centre, checked the same day, says OpenAI-built apps are search-only today and do not support write actions. For ChatGPT to save a draft or send an email, it needs a custom MCP app, such as the Kasar server.
02Kasar route: four steps, about ten minutes
- 1
Connect Gmail inside Kasar
Open the Kasar inbox, email channel, pick Gmail and authorise Kasar in the Google window. Tick send access if the assistant should be able to reply for you. This happens in Kasar, not in the chat.
- 2
Add Kasar as a custom connector in Claude
Customize, Connectors, “+ Add”, then “Add custom connector”. Call it Kasar and paste the URL below. Claude’s free plan allows one; on Team and Enterprise, an owner adds it for the whole organisation first.
- 3
Authorise your workspaces
The Kasar authorisation page opens. Tick one or more workspaces, pick the default one, then Authorize. Claude registers itself with Kasar through OAuth 2.1 with PKCE, and the token lasts 90 days.
- 4
Test with a simple question
“Which email accounts are connected to Kasar?” The assistant calls crm_manage_integrations and lists your accounts, with their send access.
The same setup in ChatGPT
In ChatGPT, the Kasar server becomes a custom MCP app: Apps, Create, then the URL, OAuth authentication and a tool scan. According to OpenAI’s help centre, full MCP, write actions included, is in beta for Business, Enterprise and Edu, on the web only, and an admin enables developer mode first. On Pro, developer mode opens the read tools: ChatGPT browses your mailbox and records, while drafts and sends happen from Claude or from Kasar.
03From request to tool: what Claude calls
“What came in this morning?”
- Tool called
- crm_mailbox
- What changes
- Nothing: a live read at Google
“Draft a reply”
- Tool called
- crm_draft
- What changes
- A draft in your Gmail Drafts, in the right thread
“Send them the proposal”
- Tool called
- crm_send_message
- What changes
- An email, after preview and confirmation
“Add them to the CRM”
- Tool called
- crm_sync_participant
- What changes
- A record created or found, the thread linked
“Remind me to follow up on Thursday”
- Tool called
- crm_manage_tasks
- What changes
- A task linked to the record
“Why isn’t this email on their record?”
- Tool called
- crm_manage_integrations
- What changes
- Nothing: the sync rules, explained
04Five prompts to try on day one
- 1
“Of my last twenty Gmail threads, which ones relate to an open deal?”
crm_mailbox lists threads with their link status; for those with a record, the assistant looks up the linked opportunity and gives you its stage.
- 2
“Read Sophie Garnier’s latest email and create a reminder task for Thursday.”
The assistant opens the thread, sums up what she asks, then crm_manage_tasks creates the task on Sophie’s record, due Thursday.
- 3
“Draft a reply to Mark in Gmail with the three points from our last meeting.”
crm_find_events reads the recorded meeting summary, and crm_draft drops the reply into your Drafts, ready to review.
- 4
“Send Leah the confirmation for Tuesday’s meeting from my work address.”
crm_send_message returns a preview with the chosen sender, subject and text; the email goes once you say yes.
- 5
“Why doesn’t Thomas’s email show on his record? Add it.”
crm_manage_integrations explains which rule left it out, then crm_sync_participant links Thomas and the thread to the CRM.
05What the assistant can read and write in your Gmail
- Read : system folders, your labels, unread mail and the full content of a thread, at the moment you ask.
- Write safely : a draft, created, updated or deleted in your Drafts folder, never sent.
- Send : a reply or a new email from the account you choose, after preview and confirmation.
- Tidy : mark a recorded thread you own as read, unread or starred.
- Link : create or find a correspondent’s record, import their history, add them to a list.
- Tune : exclude an address, a domain or subject keywords from sync, or switch to manual mode.
The assistant does not add mailboxes itself: a new address is connected in Kasar, up to one mailbox per person on Free, two on Pro and five on Max (pricing).
06A preview before every email
The first call to the send tool sends nothing. It returns the exact text, the recipients, the sending account and a confirmation token that lasts 5 minutes and works once. The email only goes on the second call, with the token. Claude is instructed to show you the preview and wait for your “yes” before that second call, and also asks you to approve the call, depending on your settings. Change a recipient in between and the token is refused: you need a fresh preview.
The server adds its own safeguards: invalid addresses rejected at preview, addresses on your workspace suppression list left out, an identical send repeated within a short window sent once, and at most 30 sends per hour per user. In ChatGPT, the app may also ask you to approve each write, depending on its permission settings.
Gmail answers “what did I get?”. The CRM answers “what does it change for the deal?”.
For the server side in detail, read the Gmail MCP server page. For Gmail inside Kasar without an assistant, the Gmail integration page. To compare with other CRMs, the CRM MCP server table.
Frequently asked questions
No, both can live in the same conversation. Say “in Kasar” when the answer should take your records and deals into account, and Claude will go through the Kasar server.
Yes, on the Kasar side: one mailbox per person on Free, two on Pro, five on Max. The assistant then asks which address to write from. Claude’s Google connector sticks to the one Google account you connected.
Claude’s OAuth token expires. Claude normally restarts the authorisation on its own; if not, reconnect the connector from Customize, Connectors. You can also revoke it at any time from Kasar.
No. The live read goes through your account, and colleagues only see emails recorded in the CRM, under the visibility you set.
Sources
Every fact on this page can be checked on the official page below, read on the date shown.
- Claude, aide : Use Google Workspace connectors · read on October 6, 2026
- Claude, aide : Get started with custom connectors using remote MCP · read on October 6, 2026
- OpenAI, aide : Developer mode and MCP apps in ChatGPT · read on October 6, 2026