fix: parse MCP result payloads and drop place idempotency_key

Typed result structs replace empty envelopes. Equity place sends
ref_id only so live additionalProperties:false schemas accept the call.

internal/wire/list.go

@@ -0,0 +1,76 @@
+package wire
+
+import (
+	"encoding/json"
+	"net/url"
+	"strings"
+)
+
+// UnmarshalRows unpacks a list from an object (trying keys in order) or a JSON array.
+// next is next_cursor, else the cursor query param of next, else next itself when it
+// is not a URL.
+func UnmarshalRows[T any](raw json.RawMessage, keys ...string) (rows []T, next string, err error) {
+	data := Unwrap(raw)
+	var obj map[string]json.RawMessage
+	if json.Unmarshal(data, &obj) != nil {
+		var list []T
+		if err := json.Unmarshal(data, &list); err != nil {
+			return nil, "", err
+		}
+		return list, "", nil
+	}
+	next = cursorFromMap(obj)
+	for _, k := range keys {
+		item, ok := obj[k]
+		if !ok || len(item) == 0 || string(item) == "null" {
+			continue
+		}
+		var list []T
+		if json.Unmarshal(item, &list) == nil {
+			return list, next, nil
+		}
+		var one T
+		if json.Unmarshal(item, &one) == nil {
+			return []T{one}, next, nil
+		}
+	}
+	return nil, next, nil
+}
+
+func cursorFromMap(obj map[string]json.RawMessage) string {
+	if c := stringField(obj, "next_cursor"); c != "" {
+		return c
+	}
+	return Cursor(stringField(obj, "next"), "")
+}
+
+func stringField(obj map[string]json.RawMessage, key string) string {
+	raw, ok := obj[key]
+	if !ok || len(raw) == 0 || string(raw) == "null" {
+		return ""
+	}
+	var s string
+	if json.Unmarshal(raw, &s) == nil {
+		return s
+	}
+	return ""
+}
+
+// Cursor prefers nextCursor; otherwise extracts cursor from a next URL.
+func Cursor(next, nextCursor string) string {
+	if nextCursor != "" {
+		return nextCursor
+	}
+	next = strings.TrimSpace(next)
+	if next == "" {
+		return ""
+	}
+	u, err := url.Parse(next)
+	if err != nil || (u.Scheme == "" && u.Host == "" && !strings.Contains(next, "?")) {
+		return next
+	}
+	if v := u.Query().Get("cursor"); v != "" {
+		return v
+	}
+	return ""
+}

internal/wire/list_test.go

@@ -0,0 +1,49 @@
+package wire_test
+
+import (
+	"encoding/json"
+	"testing"
+
+	"s1d3sw1ped/robinhood-agentic-mcp/internal/wire"
+)
+
+func TestUnmarshalRows_objectAndArray(t *testing.T) {
+	t.Parallel()
+	type row struct {
+		ID string `json:"id"`
+	}
+	rows, next, err := wire.UnmarshalRows[row](json.RawMessage(`{"data":{"positions":[{"id":"a"}],"next_cursor":"c2"}}`), "positions", "results")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(rows) != 1 || rows[0].ID != "a" || next != "c2" {
+		t.Fatalf("%+v %q", rows, next)
+	}
+	rows, next, err = wire.UnmarshalRows[row](json.RawMessage(`[{"id":"b"}]`), "positions")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(rows) != 1 || rows[0].ID != "b" || next != "" {
+		t.Fatalf("%+v %q", rows, next)
+	}
+	rows, next, err = wire.UnmarshalRows[row](json.RawMessage(`{"results":{"id":"one"},"next":"https://x/?cursor=n3"}`), "positions", "results")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(rows) != 1 || rows[0].ID != "one" || next != "n3" {
+		t.Fatalf("%+v %q", rows, next)
+	}
+}
+
+func TestCursor(t *testing.T) {
+	t.Parallel()
+	if wire.Cursor("https://x/y?cursor=abc", "") != "abc" {
+		t.Fatal("url")
+	}
+	if wire.Cursor("rawtok", "pref") != "pref" {
+		t.Fatal("pref")
+	}
+	if wire.Cursor("rawtok", "") != "rawtok" {
+		t.Fatal("bare")
+	}
+}