# FIXSIM (remote · mcp.fixsim.com)

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

- Trust score: 67/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-20

## Components

- remote · `mcp.fixsim.com`: 67/100 (this document), [markdown](https://verifymcp.io/servers/gammathreetrading-fixsim/mcp.md), [page](https://verifymcp.io/servers/gammathreetrading-fixsim/mcp)

## Channel facts

- Endpoint: `https://mcp.fixsim.com/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `0.1.2`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-09-20.

- **Endpoint Security**: 57/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation check failed: no authorisation is required to call this server, and it exposes a tool marked destructive (sandbox_end_session).
  - HTTPS is enforced; there's no plaintext access path.
  - HSTS check failed: the Strict-Transport-Security header is absent.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 79/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 2332 tokens (~111/item across 21 items; 21 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 27/100
  - Stability observed for 8 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 81/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 42% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - All 2 tool(s) whose name or description implies an irreversible operation declare an MCP destructiveHint annotation.
  - An AI judge read all 22 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the FIXSIM MCP server?

FIXSIM is a hosted endpoint at https://mcp.fixsim.com/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http gammathreetrading-fixsim 'https://mcp.fixsim.com/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "gammathreetrading-fixsim": {
      "url": "https://mcp.fixsim.com/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "gammathreetrading-fixsim": {
      "type": "http",
      "url": "https://mcp.fixsim.com/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.gammathreetrading-fixsim]
url = "https://mcp.fixsim.com/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "gammathreetrading-fixsim": {
      "type": "remote",
      "url": "https://mcp.fixsim.com/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add gammathreetrading-fixsim --url 'https://mcp.fixsim.com/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  gammathreetrading-fixsim:
    url: "https://mcp.fixsim.com/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "gammathreetrading-fixsim": {
      "Transport": "http",
      "Url": "https://mcp.fixsim.com/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add gammathreetrading-fixsim -t streamable-http -u 'https://mcp.fixsim.com/mcp'
```

### Other

```json
{
  "mcpServers": {
    "gammathreetrading-fixsim": {
      "type": "http",
      "url": "https://mcp.fixsim.com/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-09-19 (score 67, +1)

No change was recorded against any check on this day. Stability & Change Management went from 20 to 23. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 7 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-17 (score 66, +1)

No change was recorded against any check on this day. Stability & Change Management went from 13 to 17. That category is still filling its 30-day observation window: 4 days of observed history at the previous scan, 5 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-15 (score 65, +1)

No change was recorded against any check on this day. Stability & Change Management went from 7 to 10. That category is still filling its 30-day observation window: 2 days of observed history at the previous scan, 3 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-13 (score 64, 0)

- [functional improvement] Stability: unverified → 0.03
- [functional] Server version: 0.1.1 → 0.1.2
- [cosmetic] Tool “fixsim_act_on_orders” changed its title: Act on inbound orders
- [cosmetic] Tool “fixsim_cancel_order_out” changed its title: Send an Order Cancel Request
- [cosmetic] Tool “fixsim_get_order_in” changed its title: Get inbound order
- [cosmetic] Tool “fixsim_get_session” changed its title: Get FIX session
- [cosmetic] Tool “fixsim_list_executions_in” changed its title: List inbound execution reports
- [cosmetic] Tool “fixsim_list_executions_out” changed its title: List outbound execution reports
- [cosmetic] Tool “fixsim_list_instances” changed its title: List FIXSIM instances
- [cosmetic] Tool “fixsim_list_orders_in” changed its title: List inbound orders
- [cosmetic] Tool “fixsim_list_orders_out” changed its title: List outbound orders
- [cosmetic] Tool “fixsim_list_securities” changed its title: List securities
- [cosmetic] Tool “fixsim_list_sessions” changed its title: List FIX sessions
- [cosmetic] Tool “fixsim_send_order” changed its title: Send a New Order Single
- [cosmetic] Tool “fixsim_send_raw_fix” changed its title: Send raw FIX messages
- [cosmetic] Tool “sandbox_act_on_order” changed its title: Fill, reject, or cancel a sandbox order
- [cosmetic] Tool “sandbox_create_session” changed its title: Create sandbox FIX session
- [cosmetic] Tool “sandbox_end_session” changed its title: End sandbox session
- [cosmetic] Tool “sandbox_get_messages” changed its title: Read sandbox FIX message log
- [cosmetic] Tool “sandbox_get_orders” changed its title: List sandbox orders
- [cosmetic] Tool “sandbox_get_session” changed its title: Get sandbox session
- [cosmetic] Tool “sandbox_get_status” changed its title: Check sandbox connection status
- [cosmetic] Tool “sandbox_set_autofill” changed its title: Set sandbox auto-fill

### 2026-09-12 (score 64)

First indexed and scored.

## MCP tools (21)

### `fixsim_list_orders_out` (~90 tokens)

List outbound orders

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

Input parameters:

- `apiKey` (string|null)
- `clOrdId` (string|null)
- `instance` (string, required)
- `limit` (integer): Max rows to return, newest first (default 25, max 200)
- `session` (string, required)

### `sandbox_get_status` (~46 tokens)

Check sandbox connection status

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

Input parameters:

- `sessionId` (string, required)

### `fixsim_send_order` (~233 tokens)

Send a New Order Single

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.

Input parameters:

- `additionalTags` (array|null): Extra FIX tags, e.g. [{tag:59,value:"0"}]
- `apiKey` (string|null)
- `clOrdId` (string, required): ClOrdID (tag 11) to assign; must be unique on the session
- `instance` (string, required)
- `ordType` (string, required): OrdType (tag 40): 1=Market, 2=Limit
- `orderQty` (number, required): OrderQty (tag 38)
- `price` (number|null): Price (tag 44), required for limit orders
- `session` (string, required)
- `side` (string, required): Side (tag 54): 1=Buy, 2=Sell, 5=Sell short
- `symbol` (string, required): Symbol (tag 55)

### `fixsim_list_orders_in` (~151 tokens)

List inbound orders

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.

Input parameters:

- `apiKey` (string|null)
- `instance` (string, required)
- `limit` (integer): Max rows to return, newest first (default 25, max 200)
- `orderStatus` (string|null): Optional FIX OrdStatus (tag 39) filter
- `session` (string, required)

### `fixsim_list_executions_in` (~116 tokens)

List inbound execution reports

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).

Input parameters:

- `apiKey` (string|null)
- `execId` (string|null): Optional ExecID (tag 17) filter
- `instance` (string, required)
- `limit` (integer): Max rows to return, newest first (default 25, max 200)
- `session` (string, required)

### `fixsim_act_on_orders` (~222 tokens)

Act on inbound 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.

Input parameters:

- `action` (string, required): One of: Ack, FullyExecute, PartialExecute, CancelRemaining, DoneForDay, AckCancelOrdReplaceReq, AcceptCancelOrdReplaceReq, RejectCancelOrdReplaceReq, Reject, Delete, Restate, Expire
- `apiKey` (string|null)
- `clOrdIds` (array, required): ClOrdIDs (tag 11) of the inbound orders to act on
- `instance` (string, required)
- `lastPx` (number|null): Fill price (LastPx) for executions
- `lastQty` (number|null): Fill quantity (LastQty) for a partial execution
- `session` (string, required)

### `sandbox_set_autofill` (~69 tokens)

Set sandbox auto-fill

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.

Input parameters:

- `enabled` (boolean, required)
- `sessionId` (string, required)

### `fixsim_cancel_order_out` (~124 tokens)

Send an Order Cancel Request

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

Input parameters:

- `additionalTags` (array|null)
- `apiKey` (string|null)
- `clOrdId` (string, required): ClOrdID of the order to cancel (becomes OrigClOrdID, tag 41)
- `instance` (string, required)
- `newClOrdId` (string|null): New ClOrdID for the cancel request (tag 11); generated if omitted
- `session` (string, required)

### `fixsim_list_sessions` (~69 tokens)

List FIX 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.

Input parameters:

- `apiKey` (string|null)
- `instance` (string, required): Instance name from fixsim_list_instances

### `fixsim_list_executions_out` (~143 tokens)

List outbound execution reports

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.

Input parameters:

- `apiKey` (string|null)
- `clOrdId` (string|null): Optional ClOrdID (tag 11) to narrow to one order
- `instance` (string, required)
- `limit` (integer): Max rows to return, newest first (default 25, max 200)
- `session` (string, required)

### `fixsim_get_session` (~59 tokens)

Get FIX session

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

Input parameters:

- `apiKey` (string|null)
- `instance` (string, required)
- `session` (string, required): Session name from fixsim_list_sessions

### `sandbox_act_on_order` (~96 tokens)

Fill, reject, or cancel a sandbox 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.

Input parameters:

- `action` (string, required): fill, partial, reject or cancel
- `clOrdId` (string, required): ClOrdID (tag 11) of the order
- `sessionId` (string, required)

### `fixsim_get_order_in` (~89 tokens)

Get inbound order

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.

Input parameters:

- `apiKey` (string|null)
- `clOrdId` (string, required): ClOrdID, FIX tag 11
- `instance` (string, required)
- `session` (string, required)

### `sandbox_get_orders` (~47 tokens)

List sandbox orders

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

Input parameters:

- `sessionId` (string, required)

### `sandbox_get_messages` (~115 tokens)

Read sandbox FIX message log

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.

Input parameters:

- `afterSeq` (integer): Return only messages with seq greater than this
- `sessionId` (string, required)

### `sandbox_create_session` (~160 tokens)

Create sandbox FIX 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.

Input parameters:

- `fixVersion` (string): FIX.4.0, FIX.4.2, FIX.4.4 (default) or FIX.5.0SP2 (rides FIXT.1.1)

### `sandbox_end_session` (~39 tokens)

End sandbox session

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

Input parameters:

- `sessionId` (string, required)

### `fixsim_send_raw_fix` (~144 tokens)

Send raw FIX messages

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.

Input parameters:

- `apiKey` (string|null)
- `fixMessages` (array, required): Raw FIX messages, e.g. 35=D|11=ORD1|55=IBM|54=1|38=100|40=2|44=150.25|59=0
- `instance` (string, required)
- `session` (string, required)

### `fixsim_list_instances` (~72 tokens)

List FIXSIM 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.

Input parameters:

- `apiKey` (string|null): FIXSIM API key. Omit when the connector sends it as a header.

### `fixsim_list_securities` (~53 tokens)

List securities

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

Input parameters:

- `apiKey` (string|null)
- `instance` (string, required)

### `sandbox_get_session` (~45 tokens)

Get sandbox session

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

Input parameters:

- `sessionId` (string, required): Session id from sandbox_create_session

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/gammathreetrading-fixsim/mcp#diagnostics

## Score history

- 2026-09-20: 67
- 2026-09-19: 67
- 2026-09-18: 66
- 2026-09-17: 66
- 2026-09-16: 65
- 2026-09-15: 65
- 2026-09-14: 64
- 2026-09-13: 64
- 2026-09-12: 64

## Common questions

### What is the FIXSIM MCP server?

FIXSIM is an MCP server listed in the public MCP registry as io.github.GammaThreeTrading/fixsim. Test FIX from Claude, ChatGPT, or Cursor: free sandbox FIX sessions or your own FIXSIM instances. This page covers its hosted endpoint (https://mcp.fixsim.com/mcp).

### Is the FIXSIM MCP server safe to use?

FIXSIM scores 67 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the FIXSIM MCP server expose?

FIXSIM exposes 21 tools: fixsim_list_orders_out, sandbox_get_status, fixsim_send_order, fixsim_list_orders_in, fixsim_list_executions_in, and 16 more. Their descriptions and schemas cost roughly 2,182 tokens of context every time the server is loaded.

### Does the FIXSIM MCP server require authentication?

No. We connected to FIXSIM without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the FIXSIM MCP server still maintained?

FIXSIM is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://mcp.fixsim.com/mcp
- Repository: https://github.com/GammaThreeTrading/fixsim-mcp
- Website: https://www.fixsim.com/sandbox
- Changelog RSS feed: https://verifymcp.io/servers/gammathreetrading-fixsim/mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/gammathreetrading-fixsim/mcp.json
- HTML version of this page: https://verifymcp.io/servers/gammathreetrading-fixsim/mcp