MCP Airline Demo

What it is

An assistant composes three separate back-end systems over MCP to book a trip:

Each server reads its data fresh on every call. That is the whole trick: change a file between two questions and the next answer changes — no restart, no redeploy.

The data

All synthetic. Two SQLite databases and a folder of markdown — this is everything the assistant can see. Follow these rows through the simulator below.

reservations · SQLite → flights

Cheapest overall is Seattle ($118) — but it's raining. AA88 → San Diego ($149) is the cheapest that's actually sunny. DL455 → Phoenix ($129) is the trap in Beat B.

reservations · SQLite → airports (weather)

This is the current snapshot: Phoenix is a Storm today. The stale snapshot (Beat B) is the same table frozen 5 days ago — every weather_as_of reads 2026-08-17 and Phoenix still says Sunny. Same data, older date → wrong answer.

reservations · SQLite → bookings

Two seed bookings. When you click Book it in the simulator, the assistant write_querys a new BKG-60xx row here — a real write over MCP.

loyalty · SQLite → members

Jordan has plenty of miles — so the happy path applies 12,000. In Beat C this whole table is unreachable (the DB file is swapped for junk), and the query errors.

policies · filesystem → markdown

The filesystem server serves whatever is in policy/active/. A toggle swaps current ↔ stale — the RAG version of the stale-source failure.

See it happen

Each server re-reads its backend on every call, so the toggle scripts (use-stale.sh, break-miles.sh) change behavior with no restart — the point of the demo, and the source of both failures.

Want to run this for real on your machine? → open the Run it yourself tab above.

Prerequisites

• uv — runs the SQLite server: curl -LsSf https://astral.sh/uv/install.sh | sh
• Node.js — runs the filesystem server via npx
• A desktop MCP client — e.g. Claude Desktop, Claude Code, or the OpenAI Codex CLI. Any MCP-capable host works.
• Python 3 (stdlib only) — seeds the synthetic databases

1 · Clone & seed

git clone https://github.com/agnitrip/mcp-airline-demo.git
cd mcp-airline-demo
./scripts/setup.sh        # seed synthetic DBs + clean baseline
./scripts/status.sh       # -> reservations CURRENT, loyalty healthy, policies CURRENT

2 · Wire the MCP host

Add the three servers to your client's config. Replace /ABSOLUTE/PATH/TO/mcp-airline-demo with the real path — SQLite needs absolute paths.

{
  "mcpServers": {
    "reservations": {
      "command": "uvx",
      "args": ["--with", "mcp[cli]<2", "mcp-server-sqlite",
               "--db-path", "/ABSOLUTE/PATH/TO/mcp-airline-demo/data/reservations.db"]
    },
    "loyalty": {
      "command": "uvx",
      "args": ["--with", "mcp[cli]<2", "mcp-server-sqlite",
               "--db-path", "/ABSOLUTE/PATH/TO/mcp-airline-demo/data/loyalty.db"]
    },
    "policies": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem",
               "/ABSOLUTE/PATH/TO/mcp-airline-demo/policy/active"]
    }
  }
}

Claude Desktop (macOS): put this in ~/Library/Application Support/Claude/claude_desktop_config.json. Claude Code: save as .mcp.json in the project root. Then fully quit and reopen the host and confirm all three servers connect. If the host can't find uvx, use its absolute path (which uvx).

3 · The two prompts

Set the assistant's instructions to one of these (paste as Project instructions in Claude Desktop, or as the first message in Claude Code):

• assistant-base.md — naive build (Beats A, B, C). No guardrail, so a stale source or a broken tool fools it.
• assistant-guardrailed.md — same assistant + a guardrail: quote your source and fail closed on missing, errored, or stale data (Beat D).

4 · Run the four beats

Start a new chat for each beat and type the same request every time:

Book me a cheap flight somewhere sunny this weekend and use my miles. I'm Jordan Rivera.

Reset any time with ./scripts/setup.sh.