If you've asked an AI agent to "send my return to the IRS," you've probably watched it go looking for an IRS e-file API that doesn't exist. Only Authorized IRS e-file Providers can send returns to the IRS, so an agent can't post a 1040 there directly. I built Terminal Tax (terminal.tax) to be that last step. It's a hosted MCP server at https://mcp.terminal.tax/v1/hosted-mcp. No API key or install, so any agent that can make a web request can call it.
The agent sends the person's tax numbers. We calculate and check the return and send back one private link. The person opens it, reviews the return, and signs it themselves, and then we e-file it. Their SSN and signing PIN go on that page, never in the chat.
The exact requests are at https://terminal.tax/llms.txt.