MCP server

FIXSIM

io.github.GammaThreeTrading/fixsim

Checked 25 Oct 2026, 20:29 UTC · Connected to it and listed its tools

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

Website Source

At a glance

Type

MCP server

Publisher

Not verified

Status

Working at last check

Tools

21

Token cost

About 3,424 tokens per request

Sets up in

Claude Code, Claude Desktop, Codex, Gemini CLI, Cursor, VS Code, Antigravity, ChatGPT, OpenAI API, Grok

Last checked

25 Oct 2026, 20:29 UTC

Connect it to your agent

Add to CursorAdd to VS CodeVS Code Insiders

Opens the app, which shows the server and asks you to confirm. For other apps, copy the setup below.

Claude Code

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

Claude Desktop

Settings → Connectors → Add custom connector, and paste the URL.

Codex (config.toml)

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

Gemini CLI

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

Cursor

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

VS Code

{"servers":{"fixsim":{"type":"http","url":"https://mcp.fixsim.com/mcp"}}}

Antigravity

agy mcp add fixsim https://mcp.fixsim.com/mcp

ChatGPT

Settings → Apps & Connectors → Advanced settings: turn on Developer mode, then Create a connector and paste the URL. Which plans can do this varies.

OpenAI API (Responses tools)

{"type":"mcp","server_label":"fixsim","server_url":"https://mcp.fixsim.com/mcp","require_approval":"always"}

Grok (xAI API tools)

{"type":"mcp","server_label":"fixsim","server_url":"https://mcp.fixsim.com/mcp"}

Tools

• fixsim_act_on_orders ~333 tokens
  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
• fixsim_cancel_order_out ~228 tokens
  Have FIXSIM send an Order Cancel Request (35=F) for an order it previously sent out with fixsim_send_order.
• fixsim_get_order_in ~135 tokens
  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 ~111 tokens
  Get one FIX session's settings and live state (logged in?, sequence numbers, connection details).
• fixsim_list_executions_in ~182 tokens
  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 ~202 tokens
  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 ~116 tokens
  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 ~219 tokens
  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 reject
• fixsim_list_orders_out ~143 tokens
  Orders FIXSIM sent OUT on a session (created with fixsim_send_order). Pass clOrdId to fetch one.
• fixsim_list_securities ~88 tokens
  Securities (symbol, last price, CUSIP, ISIN) configured on an instance. FIXSIM prices fills from these.
• fixsim_list_sessions ~118 tokens
  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 Sends messages · ~361 tokens
  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 Sends messages · ~192 tokens
  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_act_on_order ~158 tokens
  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 ~201 tokens
  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 message
• sandbox_end_session ~75 tokens
  End a sandbox session now instead of waiting for it to expire. Frees the slot for the user's IP.
• sandbox_get_messages ~178 tokens
  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 message
• sandbox_get_orders ~84 tokens
  Working orders the user's engine has sent into the sandbox session: ClOrdID, symbol, side, qty, filled, leaves, price, status.
• sandbox_get_session ~94 tokens
  Re-fetch a sandbox session's connection card by id, including whether auto-fill is on and when it expires.
• sandbox_get_status ~87 tokens
  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 ~119 tokens
  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.

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