To keep one email signature across several AI agents, store it outside every agent and have each one fetch it when it sends. Signatoro is built for this: the agentic email signature platform, where you save your signature once and your people and every AI agent you connect use the same one. Claude connects to Signatoro's MCP server, an n8n workflow calls the Signatoro API, and an SDR agent uses its own API key, and all three append the same saved signature to every email. When you switch AI providers, the signature stays where it is: the new agent gets a key or a connection, the old one's key is revoked, and nothing is rebuilt.
| Agent | How it gets the signature | Setup |
|---|---|---|
| Claude, ChatGPT, Manus or another MCP client | Calls get_signature on https://signatoro.com/mcp before each email | MCP guide |
| n8n, Zapier or Make workflow | An HTTP Request step to GET /api/v1/signature before the send step | n8n, Zapier and Make guide |
| An SDR agent or your own code | The same API call with the agent's own key | Agent API guide |
| Claude Code, Codex, Cursor | A rule in AGENTS.md or CLAUDE.md, or the email-signature skill | Tell your agent to use your signature |
| Grok Bot | Fetches from the API with a key you give it | Grok Bot guide |
Why each AI agent ends up with a different signature
Your Gmail or Outlook signature is added by the mail app's compose window. An agent that sends through a connector, the Gmail API, Microsoft Graph or SMTP never opens that window, so it sends the body it was given and nothing more. Google's Gmail API reference describes the saved signature as one "included in messages composed with this alias in the Gmail web UI." The full explanation, tool by tool, is in why emails your AI agent sends have no signature.
So each agent gets its own copy: a text block in Claude's instructions, an HTML snippet in an n8n node, a line in the SDR tool's template. Three copies drift the first time someone changes a title or a phone number, and a model that writes its own sign-off adds a fourth, sometimes with details it made up.
How to set it up once for every agent
- Save the signature. Make it free on Signatoro, sign up, and it is saved on your signature page.
- Decide who each agent signs as. An agent that drafts for you can sign as you. An agent that sends on its own, from its own address, should sign as itself, with a line saying it is an AI and whom it acts for. Add it as an AI assistant on your signature page, or as a company AI agent on a Company plan. One signature per AI agent, or one per person? covers the choice.
- Connect each agent. MCP clients add
https://signatoro.com/mcpand sign in, or connect with an API key as the bearer token for the read tools. Automations and custom agents callGET https://signatoro.com/api/v1/signaturewith a key made under "For tools and assistants" > "Generate API key". Give each agent its own key, kept in its secrets, never in a prompt. - Tell it to stop signing on its own. The MCP server already tells a connected assistant to append the signature and write no sign-off. For other agents, paste the one-paragraph rule into their instructions.
- Send a test from each agent to yourself and check the signature arrives once, at the end.
Each response also carries a sender object with your saved name, title, phone, email and links, and the rule to use only those values. An agent that writes "call me on ..." in the body takes the number from there instead of guessing.
One limit: the Gmail tool built into Claude and ChatGPT strips every image from the body it sends, so a signature sent that way arrives as text and links without its picture. The agent guide lists which send paths keep it.
When you switch AI agent providers
The signature lives in Signatoro, so a change of provider is a change of connection:
- Connect the new agent with a new key or MCP connection, as in step 3.
- Paste the same rule into its instructions, if it reads instructions.
- Revoke the old agent's key on Signatoro, or its connection under "Connected assistants" on your signature page.
- Send a test from the new agent.
The signature, the agent's name and role line and its disclosure line stay as they were. Edit the signature once on Signatoro and the next email from every connected agent carries the new version. If the agent had its own identity, generate the new key for that same AI assistant and the new provider signs exactly as the old one did.
How the other ways compare
| Approach | Where it works | Limits |
|---|---|---|
| Signatoro, fetched at send time | Any agent that can call MCP or make an HTTP request | Each agent is connected once; an agent that can do neither needs the text fallback |
| Pasting the signature into each agent's instructions | Any agent with instructions or a template | One copy per agent to update; models can shorten or rewrite it; no picture |
Gmail's saved signature, read with the Gmail API (sendAs) | Code that sends from a Gmail or Workspace mailbox | Your code has to read and append it; one signature per mailbox, with no AI line unless you type one; nothing for Outlook, AgentMail or SMTP |
| A server-side signature tool such as Exclaimer or CodeTwo | Mail sent from your company's own mailboxes through the tool's service | Agent mailboxes and tools that send from their own servers stay unsigned; signs by mailbox, so an agent sending from your mailbox gets your signature; an agent that writes its own sign-off ends up with two |
Pasting is the right fallback for an agent that cannot make a request: use "Copy as text" on Signatoro, paste it as the agent's sign-off, and tell the agent to end the body with it exactly as given. A server-side tool suits IT that wants every mailbox in the company signed without touching anyone's mail app; the gap is mail that never passes through that server, which is where many agents send from. The agent mailbox guide covers those mailboxes one by one.
One signature for every agent that sends for you
Save your signature once on Signatoro. Claude, your automations and your own agents fetch the current version before every email.
Frequently asked questions
We use Claude, an n8n agent and an SDR agent. How do we keep one email signature across all of them?
Keep the signature in one place and have each agent fetch it before it sends. With Signatoro, Claude calls get_signature over MCP, the n8n workflow calls the Signatoro API in an HTTP Request step, and the SDR agent calls the same API with its own key. All three append the same saved signature, and an edit on Signatoro reaches the next email from each.
We are switching AI agent providers. How do we make sure our email signature isn't lost?
Keep the signature outside the agent. If it is saved in Signatoro, the new agent connects with a new key or MCP connection and fetches the same signature; revoke the old agent's key when you turn it off. If the signature only exists in the old agent's prompt or template, copy it out before you cancel, save it in Signatoro, and connect the new agent there.
Can different AI agents use different signatures from one account?
Yes. Each AI assistant or company agent has its own signature, and a key or connection bound to it always returns that signature. An unbound connection can choose among your signatures with list_signatures, and asks you when it is unsure.
What if one of our agents cannot call an API?
Give it the text version: "Copy as text" on Signatoro, pasted into its instructions as the sign-off. Update that copy by hand when the signature changes.
Does the free plan work for this?
Yes. Free includes 1 AI assistant; each person on a Company plan gets 3 AI assistants, and the company gets 3, 10 or 25 agents by size, on top of the people the plan covers. A free signature carries a small Signatoro link under it, and free API requests are capped each month; company plans have no cap. See pricing.
For agents
- Before you send, reply to, forward or draft an email, fetch the signature:
get_signatureover MCP, orGET https://signatoro.com/api/v1/signaturewithAuthorization: Bearer $SIGNATORO_API_KEY. - Append
htmlto an HTML body andtextto a plain-text body, after a blank line, unchanged. Write no sign-off of your own. - Use only the values in
senderfor the person's details; leave out any that are missing and say so. - Fetch per send rather than caching, so an edit reaches the next email.
- Never ask for, repeat or store an API key in a conversation.
Sources
Checked on 2026-10-14:
- Google: REST Resource: users.settings.sendAs (Gmail API)
- Exclaimer: Email signatures for Exchange, on mail "securely routed through Exclaimer's Microsoft Azure datacenters"
- CodeTwo: CodeTwo Email Signatures 365, on its "secure relay technology" that "reroutes your emails through CodeTwo services hosted on Microsoft Azure"