fixture: reference MCP server (echo/add/whoami); finding: arcade deploy is cloud-only

lib/mcp_server/src/mcp_server/server.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+"""arcade-eval reference MCP server.
+
+Deterministic, no-auth tools used as a shared eval fixture across categories:
+  - echo(text)  -> returns text unchanged            (protocol / curation / mixed-gateway)
+  - add(a, b)   -> a + b                              (deterministic invocation)
+  - whoami()    -> the calling user's id, server-side (per-user EXECUTION proof — cat 1/2)
+
+`whoami` reads `context.user_id`, which the Engine populates from the calling user's identity
+(the `Arcade-User-ID` header / auth-server `sub`). If a call as User A returns A and a call as
+User B returns B, the tool provably executes as the calling user.
+"""
+import sys
+from typing import Annotated
+
+from arcade_mcp_server import Context, MCPApp
+
+app = MCPApp(name="arcade_eval_ref", version="1.0.0")
+
+
+@app.tool
+def echo(text: Annotated[str, "Text to echo back"]) -> Annotated[str, "The same text"]:
+    """Echo the input text unchanged."""
+    return text
+
+
+@app.tool
+def add(
+    a: Annotated[int, "First addend"],
+    b: Annotated[int, "Second addend"],
+) -> Annotated[int, "The sum a + b"]:
+    """Add two integers."""
+    return a + b
+
+
+@app.tool
+def whoami(context: Context) -> Annotated[str, "The calling user's id as seen server-side"]:
+    """Return the calling user's identity as the server sees it (proves per-user execution)."""
+    return context.user_id or "<no user_id in context>"
+
+
+if __name__ == "__main__":
+    transport = sys.argv[1] if len(sys.argv) > 1 else "stdio"
+    app.run(transport=transport, host="127.0.0.1", port=8000)