chore: import upstream snapshot with attribution

examples/stories/legacy_elicitation/server.py

@@ -0,0 +1,47 @@
+"""Elicitation (handshake-era push style): a tool blocks on user input mid-call."""
+
+from pydantic import BaseModel
+
+from mcp.server.elicitation import AcceptedElicitation
+from mcp.server.mcpserver import Context, MCPServer
+from stories._hosting import run_server_from_args
+
+
+class Registration(BaseModel):
+    username: str
+    plan: str | None = None
+
+
+def build_server() -> MCPServer:
+    mcp = MCPServer("legacy-elicitation-example")
+
+    @mcp.tool(description="Register a new account by asking the user for their details.")
+    async def register_user(ctx: Context) -> str:
+        answer = await ctx.elicit("Please provide your registration details:", Registration)
+        if not isinstance(answer, AcceptedElicitation):
+            return f"registration {answer.action}"
+        return f"registered {answer.data.username} (plan: {answer.data.plan or 'free'})"
+
+    @mcp.tool(description="Link a third-party account by directing the user to a sign-in URL.")
+    async def link_account(provider: str, ctx: Context) -> str:
+        # elicitation_id must be unique per elicitation, not per provider — scope it to this request.
+        elicitation_id = f"link-{provider}-{ctx.request_context.request_id}"
+        answer = await ctx.elicit_url(
+            f"Sign in to {provider} to link your account",
+            url=f"https://example.com/oauth/{provider}/authorize",
+            elicitation_id=elicitation_id,
+        )
+        if answer.action != "accept":
+            return f"link {answer.action}"
+        # Out-of-band flow finished: tell the client which elicitation completed.
+        # The 2-hop `ctx.request_context.*` reach is interim; a later release shortens it.
+        await ctx.request_context.session.send_elicit_complete(
+            elicitation_id, related_request_id=ctx.request_context.request_id
+        )
+        return f"linked {provider}"
+
+    return mcp
+
+
+if __name__ == "__main__":
+    run_server_from_args(build_server)