Email signature for coding agents

Why email from a coding agent ends unsigned

A coding agent sends email through a mail MCP server. Superhuman Mail's server, for one, has setup steps for Claude Code, Codex, Cursor and Gemini CLI, works across your connected Gmail and Outlook inboxes, and by default asks for your approval before every send.

The agent writes the body and hands it to the server's send tool. Google describes the Gmail signature as one "included in messages composed with this alias in the Gmail web UI", and the sendMail tool in Microsoft's Mail MCP server takes a subject, recipients and a body. The email ends where the agent's text ends, or with a sign-off the agent made up.

The fix is one more MCP server. Signatoro holds your saved signature, and the agent fetches it before each email and appends it after the body.

Add the Signatoro MCP server

Signatoro's server is at https://signatoro.com/mcp and speaks MCP over streamable HTTP. Add it next to your mail server, and sign in to Signatoro the first time a tool asks for your account. Each line below is the vendor's documented way to add a remote server.

• Claude Code: run "claude mcp add --transport http signatoro https://signatoro.com/mcp", then type "/mcp" to sign in. Add "--scope user" to have it in every project.
• Cursor: under "mcpServers" in ~/.cursor/mcp.json, or .cursor/mcp.json for one project, add a "signatoro" entry with "url": "https://signatoro.com/mcp". Cursor supports OAuth for remote servers.
• Codex: in ~/.codex/config.toml, add a [mcp_servers.signatoro] table with url = "https://signatoro.com/mcp".
• Gemini CLI: run "gemini mcp add --transport http signatoro https://signatoro.com/mcp", then type "/mcp auth signatoro" to sign in.
• Kimi Code CLI: run "kimi mcp add --transport http --auth oauth signatoro https://signatoro.com/mcp", then "kimi mcp auth signatoro" to sign in.
• Windsurf: in Cascade's MCP menu, choose "Open MCP config file" and add a "signatoro" entry with "serverUrl": "https://signatoro.com/mcp". Cascade supports OAuth for Streamable HTTP servers.
• GitHub Copilot in VS Code: run "MCP: Add Server" in the Command Palette, give it https://signatoro.com/mcp, and save it to .mcp.json at the project root.
• Cline: on the "Remote Servers" tab, enter Signatoro as the name and https://signatoro.com/mcp as the URL, choose "Streamable HTTP" and click "Add Server". In cline_mcp_settings.json, set "type": "streamableHttp", since an entry without a type uses the legacy SSE transport.

Save the email signature rule in its instructions file

Signatoro's server tells a connected agent to fetch your signature before it sends, replies to, forwards or drafts any email. The email signature rule says the same in the file the agent reads at the start of every session, so it holds in long sessions and reaches an agent that calls the Signatoro API instead. Paste it into the file for your agent:

• Claude Code: CLAUDE.md in the project, or ~/.claude/CLAUDE.md for every project. Claude Code can also read a repository's AGENTS.md.
• Codex: AGENTS.md in the project, or AGENTS.md in ~/.codex for every project.
• Cursor: AGENTS.md in the project root, or a project rule in .cursor/rules set to "Always Apply".
• Gemini CLI: GEMINI.md in the project, or ~/.gemini/GEMINI.md for every project.
• Kimi Code CLI: AGENTS.md in the project, or .kimi/AGENTS.md.
• Windsurf: a rule in .windsurf/rules, or global_rules.md for every workspace.
• GitHub Copilot in VS Code: .github/copilot-instructions.md, or AGENTS.md.
• Cline: a Markdown file in .clinerules/ at the project root, or AGENTS.md.

Your signature, your AI assistant's or the company's

An agent sending from your own Gmail or Outlook can sign as you, with your saved signature. An agent that writes for you can sign as your AI assistant instead, with a line saying an AI sent the email.

Each AI assistant or agent gets its own key or MCP connection and signs as the person it works for or as itself, by default with a line saying it is an AI and whom it acts for. 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.

Add an AI assistant on your signature page. Under "Connected assistants", set "Signs as" to the assistant, and every email through that MCP connection carries its signature. Left on "Me", the agent picks a signature per email and asks you when it is unclear.

A script that sends from a company address, such as a support inbox, signs as a company AI agent. An owner adds one under "AI agents" in the company's menu on a Company plan and generates a key for it, and the script fetches the agent's signature from https://signatoro.com/api/v1/signature with that key.

Check one email

Before you leave the agent to send on its own, check one email in the inbox that receives it.

• Ask the agent to send a short email to an address you can read.
• Open it there and check that it ends with your Signatoro signature, once.
• Change your signature on Signatoro later, and the next email the agent sends carries the new version.

Coding agent email signature questions

Sources

Checked against each vendor's documentation on October 11, 2026.

• Claude Code: Connect Claude Code to tools via MCP
• Claude Code: How Claude remembers your project
• Cursor: Model Context Protocol
• Cursor: Rules
• OpenAI: Codex configuration reference
• OpenAI: Codex and AGENTS.md
• Gemini CLI: MCP servers
• Gemini CLI: GEMINI.md context files
• Kimi Code CLI: Model Context Protocol
• Kimi Code CLI: Agents and subagents
• Windsurf: Cascade MCP configuration
• Windsurf: Memories and rules
• VS Code: Add and manage MCP servers
• VS Code: Custom instructions
• Cline: Connecting to a remote server
• Cline: Rules
• Superhuman: Superhuman Mail MCP Server
• Superhuman: Email MCP server
• Gmail API: users.settings.sendAs
• Microsoft: Mail reference (preview)