Unable to send an action to another Jason agent - artificial-intelligence

Question

I am using Jason language to communicate between two agents. But I am unable to use send action, it gives an error.
These are my two agents,
Agent1 :-
// Agent Agent1 in project factorial3.mas2j
/* Initial goals */
!start.
/* Plans */
+!start : true
<- .print("starting..");
!query_factorial(2).
+!query_factorial(X) : true <-
.send(agent2,tell,giveme(X)).
/*+fact(X,Y) : true <-
.print("factorial ", X, " is ", Y, " thank you expert").*/
Agent2:-
// Agent agent2 in project IdEx.mas2j
/* Initial beliefs and rules */
/* Initial goals */
!begin.
/* Plans */
+!begin : true
<- .print("expert starting.......");
!giveme(X).
+!giveme(X):true
<- !fact(X,Y);
.print("Factorial of ", X, " is ", Y).
//.send(agent1,achive,fact(X,Y)).
+!fact(X,1) : X == 0.
+!fact(X,Y) : X > 0
<- !fact(X-1,Y1);
Y = Y1 * X.
So, I am getting an error when I am trying to call send action in agent1 and agent2 gives an receive error.
UPDATED
I am getting this error,
[agent2] *** Error adding var into renamed vars. var=X, value=(_229-1).
java.lang.ClassCastException: jason.asSyntax.ArithExpr cannot be cast to jason.asSyntax.VarTerm
at jason.asSemantics.TransitionSystem.prepareBodyForEvent(TransitionSystem.java:877)
at jason.asSemantics.TransitionSystem.applyExecInt(TransitionSystem.java:728)
at jason.asSemantics.TransitionSystem.applySemanticRule(TransitionSystem.java:222)
at jason.asSemantics.TransitionSystem.reasoningCycle(TransitionSystem.java:1429)
at jason.infra.centralised.CentralisedAgArch.run(CentralisedAgArch.java:205)
at java.lang.Thread.run(Thread.java:745)

Answer 1

If you want to ask for an agent to perform a plan (in case of agent1 when you say "+!query_factorial(X)...") it should be an achieve message. Uncommenting the "plan" "+fact(X,Y) : true <- .print("factorial ", X, " is ", Y, " thank you expert")." you should use the operator "!" at the begining to make it a plan. So, if I undertood the general idea of your test project, it can be rewrite as follows:
Agent1 code:
!start.
+!start : true
<- .print("starting..");
!query_factorial(2).
+!query_factorial(X) : true <-
.send(agent2,achieve,giveme(X)).
Agent2 code:
+!giveme(X):true
<- !fact(X,Y);
.print("Factorial of ", X, " is ", Y).
+!fact(X,1) : X == 0.
+!fact(X,Y) : X > 0
<- !fact(X-1,Y1);
Y = Y1 * X.
You can see, I am not using the "begin plan" of your original code since the Agent1 is doing the job, making Agent2 work when asked.