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"