FIXSIM MCP Server

by gammathreetrading Your server? Claim it

answering

FIXSIM is answering right now. Last checked 8 min ago. It exposes 21 tools. Last commit 13 Sep 2026.

Test FIX from Claude, ChatGPT, or Cursor: free sandbox FIX sessions or your own FIXSIM instances.

Uptime history 6 days of history

6 days agonow

100.0%

Uptime 24h

92 of 92 checks

Tools

read from the server

681 ms

Response time

average over 24h

Stars

last commit 13 Sep 2026

What changed 1

Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 13 September 2026. No other catalogue keeps this.

13 Sep a tool changed version

Nothing serious here today

Today is the operative word: we check FIXSIM every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 8 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add fixsim --transport http https://mcp.fixsim.com/mcp

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "fixsim": {
      "url": "https://mcp.fixsim.com/mcp"
    }
  }
}

~/.codex/config.toml

[mcp_servers.fixsim]
url = "https://mcp.fixsim.com/mcp"

.cursor/mcp.json

{
  "mcpServers": {
    "fixsim": {
      "url": "https://mcp.fixsim.com/mcp"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "fixsim": {
      "url": "https://mcp.fixsim.com/mcp"
    }
  }
}

Available tools 21

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

fixsim

fixsim_act_on_orders

Respond to orders the user's system sent into FIXSIM: acknowledge, fully or partially execute, reject, cancel remaining, expire, done-for-day, restate, or accept/reject a pending cancel/replace. FIXSIM emits the matching execution reports on the FIX session. Give one or more ClOrdIDs; for executions supply lastPx and, for a partial, lastQty.

fixsim_cancel_order_out

Have FIXSIM send an Order Cancel Request (35=F) for an order it previously sent out with fixsim_send_order.

fixsim_get_order_in

Get one inbound order by ClOrdID (tag 11), including its raw FIX message and audit trail. Use this to explain why an order was rejected or what state it is in.

fixsim_get_session

Get one FIX session's settings and live state (logged in?, sequence numbers, connection details).

fixsim_list_executions_in

Execution reports the user's system sent INTO FIXSIM on a session (when FIXSIM is the order sender and the user's system is the executing side). Optionally filter by ExecID (tag 17).

fixsim_list_executions_out

Execution reports FIXSIM sent OUT on a session (acks, fills, partial fills, rejects, cancels). Pass clOrdId to see the full execution history of one order: ExecType, OrdStatus, LastPx/LastQty, CumQty, LeavesQty, AvgPx and the raw FIX.

fixsim_list_instances

List the FIXSIM instances your API key can access. An instance is a hosted FIX engine; each holds one or more FIX sessions. Start here to learn the instance names other tools need.

fixsim_list_orders_in

Orders the user's trading system sent INTO FIXSIM on a session (FIXSIM is the counterparty). Includes ClOrdID, symbol, side, quantity, remaining quantity, order status and the raw FIX message. Optionally filter by FIX OrdStatus code (tag 39): 0 new, 1 partially filled, 2 filled, 4 canceled, 8 rejected.

fixsim_list_orders_out

Orders FIXSIM sent OUT on a session (created with fixsim_send_order). Pass clOrdId to fetch one.

fixsim_list_securities

Securities (symbol, last price, CUSIP, ISIN) configured on an instance. FIXSIM prices fills from these.

fixsim_list_sessions

List the FIX sessions on an instance with their FIX version, CompIDs, acceptor/initiator role, host/port, enabled and logged-in state, and sequence numbers.

fixsim_send_order

Have FIXSIM send a New Order Single (35=D) OUT on a session to the user's system, so they can test how their system handles inbound orders. Follow up with fixsim_list_orders_out and fixsim_list_executions_in to see what came back.

fixsim_send_raw_fix

Send one or more raw FIX application messages OUT on a session as given (tag=value pairs separated by | or SOH). FIXSIM supplies the session header fields (BeginString, CompIDs, MsgSeqNum, SendingTime) and the checksum. Use for message types the other tools do not cover.

sandbox

sandbox_act_on_order

Play the exchange for one order the user sent in: fill (full execution), partial (partial fill), reject, or cancel (cancel the remaining quantity). FIXSIM sends the matching execution report back to the user's engine.

sandbox_create_session

Create a free, anonymous FIX test session on the FIXSIM Developer Sandbox. No account or API key needed. Returns the connection card: host, port, the SenderCompID the user must put in tag 49, the TargetCompID for tag 56, BeginString, and the expiry (sessions last 4 hours, cap 100 application messages per day). The user's FIX engine connects as the initiator; FIXSIM is the acceptor and acknowledges every order. Keep the returned id; every other sandbox tool needs it.

sandbox_end_session

End a sandbox session now instead of waiting for it to expire. Frees the slot for the user's IP.

sandbox_get_messages

The FIX message log for a sandbox session, oldest first: logons, heartbeats, orders in, execution reports out, rejects. Each message has seq, timeUtc, inbound (true = user's engine sent it), msgType, raw FIX, and parsed tag/value fields. Pass afterSeq (the last seq you saw) to fetch only new messages. Use this to explain what happened on the wire.

sandbox_get_orders

Working orders the user's engine has sent into the sandbox session: ClOrdID, symbol, side, qty, filled, leaves, price, status.

sandbox_get_session

Re-fetch a sandbox session's connection card by id, including whether auto-fill is on and when it expires.

sandbox_get_status

Is the user's FIX engine connected to the sandbox session? Returns state: connected, waiting (nobody logged on yet), disabled, or unknown.

sandbox_set_autofill

Turn automatic fills on or off for a sandbox session. On: every order the user sends is filled immediately at the security's last price. Off (default): orders are acknowledged and wait for sandbox_act_on_order.

Endpoints

URL	Transport	State	Latency	Checked
https://mcp.fixsim.com/mcp	streamable-http	answering	731 ms	8 min ago

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FIXSIM — questions

Answers built from our own checks of this server.

What can FIXSIM do?

It exposes 21 tools, read directly from the server on our last check. Among them: fixsim_act_on_orders, fixsim_cancel_order_out, fixsim_get_order_in, fixsim_get_session, fixsim_list_executions_in, fixsim_list_executions_out and 15 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

What is FIXSIM mostly used for?

Its tools cluster around fixsim and sandbox. That is what this server is built to work with — the grouping comes from the actual tool names, not from a category we assigned.

Is FIXSIM working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 92 of 92 checks got a reply (100.0%), average response time 681 ms. The bar chart above shows every period we have measured.

How do I connect FIXSIM?

Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does FIXSIM need an API key?

No. FIXSIM completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 21 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is FIXSIM?

It answers our handshake in 681 ms on average, which is faster than 17% of all working MCP servers we measure. That is on the slow side — worth knowing if the tool sits inside an interactive loop. The comparison comes from our own checks across the whole registry, every 15 minutes.

Is FIXSIM open source?

Yes — it is published under the MIT licence, written in C# and 0 stars on GitHub. The source link is on this page, so you can read exactly what it does with your data before you connect it.