Spec Driven Development
by formulahendry
MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.
Runs on your computer★ 440MITUpdated 14 months ago
Install
FIXSIM
Overview
Description from the maker (original English)
Test FIX from Claude, ChatGPT, or Cursor: free sandbox FIX sessions or your own FIXSIM instances.
PopNx MCP’s three pillars
These three are never merged into one score: opinions, measurements and popularity are different things.
- User voiceiNo reviews yetReviews open together with accounts in a later step
- Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
- UsageiNot measured yet★ –
What you can do with it
We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.
- Connection: Runs in the cloud
- Transport: Streamable HTTP
- Category: Other
- You need to fill in: x-api-key
Install
Pick the AI app you use, then copy the settings.
Before you install
- Basic checks: 1 of 1 passed
- Runs on the maker’s server: what you ask it goes through their server.
- You fill in yourself:
x-api-key
Values marked secret are keys to your account. Never share them or paste them into a chat.
You need
- Runs in the cloudNothing to install; it connects over the internet
Which app do you use?
Pick your app above. We remember it, so next time the button says “Install in …”.
This address needs a key in a request header, which the add-connector menu cannot set. Use Claude Code, Cursor or VS Code instead.
Run this in your terminal
claude mcp add --transport http fixsim https://mcp.fixsim.com/mcp --header 'x-api-key: your-value'Fill in the empty values before running it.
Or copy the settings yourself
Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json
{
"mcpServers": {
"fixsim": {
"url": "https://mcp.fixsim.com/mcp",
"headers": {
"x-api-key": "your-value"
}
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
Or copy the settings yourself
Paste into .vscode/mcp.json in your project
{
"servers": {
"fixsim": {
"type": "http",
"url": "https://mcp.fixsim.com/mcp",
"headers": {
"x-api-key": "your-value"
}
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
This address needs a key in a request header, which the add-connector menu cannot set. Use Claude Code, Cursor or VS Code instead.
Your choice stays on this device in a cookie; no account needed.
Values you fill in
x-api-keysecret HTTP headerOptional. Your FIXSIM API key (portal.fixsim.com, API Keys). Leave blank to use only the free sandbox tools.
These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.
What it can do
We have not read this server’s tool list yet; we check endpoints in rotation.
Basic checksi
We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026
- ✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account GammaThreeTrading, which owns the repo
- … Not checked yet
Still maintained
We have not read this repo from GitHub yet
- … Not checked yet
Has a licence
We have not read this repo from GitHub yet
- … Not checked yet
Endpoint responds
Not checked yet; we check endpoints in rotation
- … Not checked yet
Sign-in with OAuth
Not checked yet; we check endpoints in rotation
- … Not checked yet
No hidden instructions in tool descriptions
Not checked yet; we read the tool list when we check the endpoint
Compared with others in Otheri
- More stars than 0% of the other 32680 servers in this category
- Published to the registry more recently than 42% of the other 32680 servers in this category
- Basic checks equal to or better than 100% of the other 32680 servers in this category
Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.
Common questions
Is FIXSIM safe?
It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.
What keys or codes does it need?
You need to fill in: x-api-key
Does it run on my computer or in the cloud?
It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.
Is it still maintained?
The GitHub repo last changed –, and the latest version (0.1.2) reached the registry 2 months ago.
Which apps can use it?
Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.
What can I use instead?
In the same category: Spec Driven Development, Remote Desktop Commander, EmbeddedCI BenchPod
Alternatives
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README from the maker
Open the README
Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.
fixsim-mcp
An MCP server for FIXSIM, the hosted FIX protocol simulator. Add it to Claude, Cursor, VS Code, or ChatGPT and test FIX from a conversation:
"Create a FIX 4.4 test session for me, then tell me when my engine has logged on and show me the first order it sent."
Two tool families live on one endpoint:
| Tools | Who | Auth |
|---|---|---|
sandbox_* | anyone | none. Free, anonymous, 4-hour sessions on the Developer Sandbox |
fixsim_* | FIXSIM customers | your FIXSIM API key, sent as an x-api-key header |
Connect
Hosted endpoint: https://mcp.fixsim.com/mcp (read-only variant: https://mcp.fixsim.com/mcp/readonly).
Claude Code
claude mcp add --transport http fixsim https://mcp.fixsim.com/mcp --header "x-api-key: YOUR_FIXSIM_API_KEY"Leave off --header if you only want the free sandbox tools.
Cursor / VS Code (mcp.json)
{"mcpServers": { "fixsim": { "url": "https://mcp.fixsim.com/mcp", "headers": { "x-api-key": "YOUR_FIXSIM_API_KEY" } } } }
Claude.ai / Claude Desktop: Customize → Connectors → Add custom connector → URL https://mcp.fixsim.com/mcp. Choose authentication *None* for the sandbox. To use your own instances, add a request header x-api-key (header support in the connector dialog is rolling out; if you do not see it, use Claude Code or Cursor for now).
Tools
Sandbox (no auth)
| Tool | What it does |
|---|---|
sandbox_create_session | Provision a free FIX session. Returns host, port, SenderCompID (your tag 49), TargetCompID (tag 56), BeginString, expiry. |
sandbox_get_status | Is your engine connected? connected / waiting / disabled. |
sandbox_get_messages | The FIX message log, raw and parsed. Pass afterSeq to poll for new messages. |
sandbox_get_orders | Working orders your engine sent in. |
sandbox_act_on_order | Play the exchange: fill, partial, reject, cancel. |
sandbox_set_autofill | Fill every incoming order automatically. |
sandbox_get_session | Re-fetch the connection card. |
sandbox_end_session | End the session early. |
Sandbox limits: 100 application messages per session per day, 4-hour sessions, a handful of sessions per caller.
FIXSIM instances (API key)
| Tool | What it does |
|---|---|
fixsim_list_instances | Instances your key can access. Start here. |
fixsim_list_sessions, fixsim_get_session | Sessions on an instance: FIX version, CompIDs, role, logged-in state, sequence numbers. |
fixsim_list_orders_in, fixsim_get_order_in | Orders your system sent into FIXSIM, with raw FIX and audit trail. |
fixsim_list_executions_out | Execution reports FIXSIM sent you (acks, fills, rejects). Filter by ClOrdID. |
fixsim_list_orders_out, fixsim_list_executions_in | The reverse direction, when FIXSIM is the order sender. |
fixsim_list_securities | Symbols and prices on an instance. |
fixsim_act_on_orders | Ack, fill, partially fill, reject, cancel, expire… orders your system sent in. |
fixsim_send_order | Have FIXSIM send you a New Order Single. |
fixsim_cancel_order_out | Have FIXSIM cancel an order it sent. |
fixsim_send_raw_fix | Send any raw FIX message on a session. |
The /mcp/readonly endpoint exposes the same tools but refuses the ones that send.
Every fixsim_* call is checked against the instances your key is entitled to, and is rate-limited per key (120 calls per minute by default).
Run it yourself
Requires .NET 8.
dotnet run --project src/FixSim.Mcp --urls http://localhost:5199Configuration (appsettings.json or environment variables such as FixSim__BaseUrl):
| Key | Default | Meaning |
|---|---|---|
FixSim:BaseUrl | https://portal.fixsim.com/ | The FIXSIM site whose /v1 API the fixsim_* tools call |
FixSim:PerKeyCallsPerMinute | 120 | Per-key rate limit at this server |
Sandbox:Enabled | true | Register the sandbox_* tools |
Sandbox:BaseUrl | https://sandbox.fixsim.com/ | The Developer Sandbox web app |
Sandbox:CallerKey | empty | Shared secret sent as X-Sandbox-Caller so the sandbox can trust server-to-server calls |
The server is stateless (Streamable HTTP), so it scales horizontally behind any load balancer.
How it works
The server is a thin client. fixsim_* tools call the public FIXSIM REST API (/v1/...) with your key; sandbox_* tools call the Developer Sandbox's session API. Nothing is stored here beyond a one-minute cache of which instances a key may access. Your API key is forwarded to FIXSIM on each call and never logged.
License
MIT