version: "1.0"
# MCP Server Metadata
server:
name: "loopExample"
version: "1.0.0"
title: "Loop Example"
instructions: "This example demonstrates loops and execution history functions like $executionCount() and $nodeExecution()."
# Tool Definitions
tools:
- name: "sum_to_n"
description: "Sums numbers from 1 to n using a loop"
inputSchema:
type: "object"
properties:
n:
type: "number"
description: "The number to sum to"
required:
- n
outputSchema:
type: "object"
properties:
sum:
type: "number"
description: "The sum from 1 to n"
nodes:
# Entry node: Receives tool arguments
- id: "entry_sum"
type: "entry"
next: "increment_node"
# Increment counter and add to sum
# Uses $nodeExecution() to get the previous iteration of this node
# First iteration: $executionCount("increment_node") = 0, so we initialize
# Subsequent iterations: $nodeExecution("increment_node", -1) gets the last execution
- id: "increment_node"
type: "transform"
transform:
expr: |
$executionCount("increment_node") = 0
? {
"counter": 1,
"sum": 1,
"target": $.entry_sum.n
}
: {
"counter": $nodeExecution("increment_node", -1).counter + 1,
"sum": $nodeExecution("increment_node", -1).sum + $nodeExecution("increment_node", -1).counter + 1,
"target": $.entry_sum.n
}
next: "check_condition"
# Check if we should continue looping
- id: "check_condition"
type: "switch"
conditions:
- rule:
"<": [{"var": "$.increment_node.counter"}, {"var": "$.increment_node.target"}]
next: "increment_node"
next: "exit_sum" # Default: exit when counter >= target
# Exit node: Extracts the sum from increment_node
# Uses $previousNode() to verify it returns the switch node's output (target node ID)
# The output matches the tool's outputSchema (just the sum)
- id: "exit_sum"
type: "transform"
transform:
expr: |
$previousNode() = "exit_sum" ? {
"sum": $.increment_node.sum
} : {
"sum": 0,
"error": "previousNode check failed"
}
next: "exit_sum_final"
# Final exit node
- id: "exit_sum_final"
type: "exit"
