email-signature

Before sending, replying to, forwarding or drafting any email for the user, with any mail tool (Gmail, Outlook, SMTP or a mail API), fetch their saved email signature from Signatoro and append it after the body. Use it every time you are about to send or draft an email, even when the user does not mention a signature. Works with the Signatoro MCP server (get_signature, list_signatures) or the REST API (GET https://signatoro.com/api/v1/signature with SIGNATORO_API_KEY).

The user's email signature is saved on Signatoro. Every email you send or draft for them carries it.

With the Signatoro MCP server

When a Signatoro get_signature tool is available:

1. Call get_signature before any send, reply, forward or draft tool, for every email, fetching it fresh each time.
2. Append the result after the body and a blank line: html for an HTML body, text for a plain-text body. Add it as returned.
3. Do not write your own sign-off or signature block.
4. For the user's own name, title, phone, email or links anywhere in the body, use only the values in sender. If one is missing, leave it out and tell the user - never guess.
5. If the user has AI assistants or company AI agents with their own signatures and it is unclear which one this email should carry, call list_signatures and ask before sending. Pass their choice to get_signature as signature.

With the REST API

When there is no Signatoro MCP tool and SIGNATORO_API_KEY is set in the environment:

bash

curl -s https://signatoro.com/api/v1/signature \
  -H "Authorization: Bearer $SIGNATORO_API_KEY"

The JSON reply has the same html, text and sender, and the same rules apply. Read the key from the environment and keep it out of output, logs, files and the conversation. ?mode=short returns the name, role line and one link; ?signature=<agent id or name> returns the signature of one of the user's AI assistants or company AI agents.

With neither available, send without a signature block, tell the user, and point them to https://signatoro.com/docs/install-signature/agent.

Troubleshooting

• The picture is missing. The Gmail and Outlook tools built into chat assistants strip every image from an HTML body. Send text through those tools; the picture needs a raw MIME send (Gmail API messages.send, SMTP).
• 401 missing_api_key or invalid_api_key: no key, a wrong key or a revoked one. Stop and tell the user.
• 403 identity_unavailable: the AI assistant or company agent behind the key was deleted or is no longer theirs. Send without a signature and tell the user.
• 404 no_signature: nothing saved yet. Send without one.
• 400 unknown_signature: signature named none of theirs. Pick one from choices.
• 429 quota_exceeded: a free account past its monthly requests. Send without the signature and tell the user.