chore: import upstream snapshot with attribution

examples/stories/legacy_elicitation/server_lowlevel.py

@@ -0,0 +1,70 @@
+"""Elicitation (handshake-era push style) against the low-level Server."""
+
+from typing import Any
+
+import mcp_types as types
+
+from mcp.server.context import ServerRequestContext
+from mcp.server.lowlevel import Server
+from stories._hosting import run_server_from_args
+
+REGISTRATION_SCHEMA: types.ElicitRequestedSchema = {
+    "type": "object",
+    "properties": {
+        "username": {"type": "string"},
+        "plan": {"type": "string", "enum": ["free", "pro", "team"]},
+    },
+    "required": ["username"],
+}
+LINK_INPUT_SCHEMA: dict[str, Any] = {
+    "type": "object",
+    "properties": {"provider": {"type": "string"}},
+    "required": ["provider"],
+}
+
+
+def build_server() -> Server[Any]:
+    async def list_tools(
+        ctx: ServerRequestContext[Any], params: types.PaginatedRequestParams | None
+    ) -> types.ListToolsResult:
+        return types.ListToolsResult(
+            tools=[
+                types.Tool(
+                    name="register_user", description="Register a new account.", input_schema={"type": "object"}
+                ),
+                types.Tool(
+                    name="link_account", description="Link a third-party account.", input_schema=LINK_INPUT_SCHEMA
+                ),
+            ]
+        )
+
+    async def call_tool(ctx: ServerRequestContext[Any], params: types.CallToolRequestParams) -> types.CallToolResult:
+        if params.name == "register_user":
+            answer = await ctx.session.elicit_form(
+                "Please provide your registration details:", REGISTRATION_SCHEMA, related_request_id=ctx.request_id
+            )
+            if answer.action != "accept" or answer.content is None:
+                return types.CallToolResult(content=[types.TextContent(text=f"registration {answer.action}")])
+            text = f"registered {answer.content['username']} (plan: {answer.content.get('plan') or 'free'})"
+            return types.CallToolResult(content=[types.TextContent(text=text)])
+
+        assert params.name == "link_account" and params.arguments is not None
+        provider = params.arguments["provider"]
+        # elicitation_id must be unique per elicitation, not per provider — scope it to this request.
+        elicitation_id = f"link-{provider}-{ctx.request_id}"
+        answer = await ctx.session.elicit_url(
+            f"Sign in to {provider} to link your account",
+            url=f"https://example.com/oauth/{provider}/authorize",
+            elicitation_id=elicitation_id,
+            related_request_id=ctx.request_id,
+        )
+        if answer.action != "accept":
+            return types.CallToolResult(content=[types.TextContent(text=f"link {answer.action}")])
+        await ctx.session.send_elicit_complete(elicitation_id, related_request_id=ctx.request_id)
+        return types.CallToolResult(content=[types.TextContent(text=f"linked {provider}")])
+
+    return Server("legacy-elicitation-example", on_list_tools=list_tools, on_call_tool=call_tool)
+
+
+if __name__ == "__main__":
+    run_server_from_args(build_server)