FireDAC does not support (unified) fetching DDL definitions of stored procedures (at this time). So, you'll need to fetch that DDL from the RDB$PROCEDURES table, RDB$PROCEDURE_SOURCE column by yourself. For example (not ideally designed as a connection object helper though):
uses
FireDAC.Stan.Util;
type
TFDConnectionHelper = class helper for TFDConnection
public
function GetStoredProcCode(const AName: string): string;
end;
implementation
{ TFDConnectionHelper }
function TFDConnectionHelper.GetStoredProcCode(const AName: string): string;
var
Table: TFDDatSTable;
Command: IFDPhysCommand;
begin
CheckActive;
if RDBMSKind <> TFDRDBMSKinds.Firebird then
raise ENotSupportedException.Create('This feature is supported only for Firebird');
Result := '';
ConnectionIntf.CreateCommand(Command);
Command.CommandText := 'SELECT RDB$PROCEDURE_SOURCE FROM RDB$PROCEDURES WHERE RDB$PROCEDURE_NAME = :Name';
Command.Params[0].DataType := ftString;
Command.Params[0].Size := 31;
Command.Params[0].AsString := UpperCase(AName);
Table := TFDDatSTable.Create;
try
Command.Define(Table);
Command.Open;
Command.Fetch(Table);
if Table.Rows.Count > 0 then
Result := Table.Rows[0].GetData(0);
finally
FDFree(Table);
end;
end;
Usage then (when you're connected to Firebird DBMS):
procedure TForm1.Button1Click(Sender: TObject);
var
S: string;
begin
S := FDConnection1.GetStoredProcCode('MyProcedure');
...
end;