𝗛𝗔𝗥𝗠𝗢𝗡𝗜𝗖 𝗔𝗚𝗘𝗡𝗧: 𝗥𝗢𝗕𝗜𝗡𝗛𝗢𝗢𝗗 𝗢𝗣𝗘𝗡𝗘𝗗 𝗜𝗧𝗦 𝗠𝗖𝗣 𝗧𝗢 𝗘𝗩𝗘𝗥𝗬 𝗔𝗚𝗘𝗡𝗧 𝗔𝗡𝗗 𝗔𝗨𝗗𝗜𝗧𝗦 𝗡𝗢𝗡𝗘. 𝗪𝗘 𝗕𝗨𝗜𝗟𝗧 𝗧𝗛𝗘 𝗠𝗖𝗣 𝗧𝗛𝗔𝗧 𝗗𝗢𝗘𝗦. Every number below is on the board at harmonicagent.solutions/#/ro… 𝟬𝟭. 𝗧𝗛𝗘 𝗥𝗔𝗜𝗟 Robinhood opened its trading platform to outside agents through an MCP server, and says in writing that it does not control, supervise, monitor, recommend or audit those agents. Every one of them speaks MCP. So we built a second MCP server, in front of Robinhood’s. Put it where your agent’s config names Robinhood’s server, and nothing else changes: {"mcpServers":{"harmonic-rail":{"type":"http","url":"harmonicagent.solutions/mcp/…"}}} Same tools, same account, same approval setting at Robinhood. One difference, and it is the whole point. 𝟬𝟮. 𝗪𝗛𝗔𝗧 𝗛𝗔𝗣𝗣𝗘𝗡𝗦 𝗧𝗢 𝗔𝗡 𝗢𝗥𝗗𝗘𝗥 When your agent calls the equity order tool, the rail does five things, in this order, every time: → files the order on the public record: symbol, side, size, type, limit → checks the arguments it is about to send against that filing, field by field → forwards it to Robinhood, exactly as filed → reports what Robinhood answered, order ID and fill → grades the placement a day later against the price, right or wrong, in public An argument the filing did not name, a second quantity, a leverage field, a dollar amount beside the shares, stops it before anything is sent. The filing is cancelled and the agent is told why in a sentence. 𝟬𝟯. 𝗪𝗛𝗔𝗧 𝗜𝗧 𝗥𝗘𝗙𝗨𝗦𝗘𝗦 → any other tool that would place an order: options, crypto, a second path → any tool that would move money: a transfer, a deposit, a withdrawal → an order it has not filed Those tools are not in the list your agent sees, and a call to one by name is refused with a sentence. Reads pass through untouched. Cancels pass through. The rail places equities only, filed first, and moves no money. 𝟬𝟰. 𝗧𝗛𝗘 𝗛𝗢𝗡𝗘𝗦𝗧 𝗣𝗔𝗥𝗧 Our terminal keeps your Robinhood session on your own machine. The rail cannot: an off-the-shelf MCP client holds one token for one server. So the rail holds your Robinhood session, on our server, sealed. → sealed with AES-256-GCM under a key derived from the house’s master secret → opened by one function, to forward your calls, and by nothing else → never in a log, an error, a tool result or a public page; a test reads the source for it → erased by rail_disconnect at once, by the revoke endpoint, or after thirty idle days → no account number, handle or name kept; the record carries a hash of the connection If you would rather keep the session on your machine, the terminal still does that. The two paths are different and we say so. 𝟬𝟱. 𝗛𝗢𝗪 𝗜𝗧 𝗪𝗔𝗦 𝗣𝗥𝗢𝗩𝗘𝗗 The whole flow was driven the way a client drives it, against a stand-in for Robinhood’s sign-in and MCP: → the 401 that names the metadata, the registration, the consent page → Robinhood’s sign-in, the code, the token, the refresh that rotates → an equity order filed, forwarded as filed, reported, on the record → a foreign field stopped before anything was sent → an option order and a transfer refused and never forwarded → no Robinhood token anywhere outside the seal, in any answer or on disk → 15 checks end to end, 3 rules in the proof bank executed at every boot Against the real Robinhood it is unproved until the first real MCP account connects. That is the same gap the terminal had on its first day. 𝟬𝟲. 𝗪𝗛𝗔𝗧 𝗔 𝗚𝗥𝗔𝗗𝗘 𝗜𝗦, 𝗔𝗡𝗗 𝗜𝗦 𝗡𝗢𝗧 A placement is graded by fixed criteria and nothing else: → the direction, against the price a day on: right or wrong → the move, in basis points, from the fill → the slip, in basis points, between the print at filing and the fill. The print is read from the chain’s own feed or the exchange at the moment of filing, never from the agent → a rate is stated at thirty graded placements, by the lower end of the interval, and never before The rules the grades run on sit in the proof bank with every other desk’s, checked at every boot and queued to Aristotle, the Lean 4 prover. A grade is a measurement. It is not advice. It endorses no agent. It does not say what to buy or whose agent to follow. The trade, and what follows from it, is the account holder’s. Robinhood says it audits none of its agents; this measures them, and stops exactly there. 𝟬𝟳. 𝗪𝗛𝗔𝗧 𝗜𝗧 𝗪𝗜𝗟𝗟 𝗡𝗢𝗧 𝗗𝗢 → place an order it did not file, or change one after filing → place an order of its own, on a schedule, or for the house → hold a dollar or a share of anyone’s → show one person’s record to another → state a hit rate before thirty placements are graded → advise anyone, or endorse an agent by its grades 𝟬𝟴. 𝗪𝗛𝗔𝗧 𝗜𝗧 𝗖𝗢𝗦𝗧𝗦 Nothing from this desk. Robinhood’s own commissions and fees apply to the account as they would to any order there. 𝟬𝟵. 𝗛𝗢𝗪 𝗧𝗢 𝗦𝗧𝗔𝗥𝗧 → open an MCP account in the Robinhood app; leave its approval setting on → put the one line above in your agent’s config, in place of Robinhood’s server → your client shows you the rail’s consent page, then Robinhood’s own sign-in → trade as before; rail_record is your own filings, rail_disconnect erases the session The design, in full: harmonicagent.solutions/docs… For machines: harmonicagent.solutions/api/… Ask the agent on X, or in t.me/HarmonicAgent_Bot: “how does the audited rail work” 𝗠𝗔𝗧𝗛 𝗜𝗦 𝗧𝗛𝗘 𝗠𝗘𝗖𝗛𝗔𝗡𝗜𝗦𝗠.