Scala — 128 Operations for AI Agents

This page is the canonical reference an AI coding agent uses to refactor, query, and analyze Scala code through the act MCP server. 128 operations available: 54 refactor, 18 query, 42 analysis, 14 verification. Each operation is callable from Claude Code, Cursor, Codex, OpenCode, or any MCP-compatible agent host. Click any operation for a stable anchor link suitable for citation.

Worked Scala examples

act101 parses Scala with the tree-sitter grammar and edits class members, sealed hierarchies, and declarations as syntax nodes, so a visibility change or generated subclass lands on the exact declaration it targets. It can tighten a method's visibility by inserting private or protected in front of its def. It can generate an empty case object subclass for each name given, extending a sealed trait or sealed abstract class, or generate a single case class subclass with named fields at a chosen position among the existing subclasses. It can replace a var declaration with val in place, without touching the initializer. And it can convert an if/else whose branches return values into a match expression with one case per branch plus a default. Each example below is the verbatim output of the command shown, run against the file shown.

Make a method private

mathutils.scala's Main class defines add with no explicit access modifier.

$ act refactor-lang add_access_modifier --file mathutils.scala --params '{"modifier":"private","line":2,"column":3}'

Before

class Main {
  def add(a: Int, b: Int): Int = a + b
}

After

class Main {
  private def add(a: Int, b: Int): Int = a + b
}

private is inserted directly before def add, hiding the method from callers outside the class.

Generate case objects for a sealed trait

shapes.scala declares sealed trait Shape with no subclasses yet.

$ act refactor-lang generate_sealed_subclasses --file shapes.scala --params '{"subclass_names":"Circle,Square,Triangle","line":1,"column":1}'

Before

sealed trait Shape

After

sealed trait Shape
case object Circle extends Shape
case object Square extends Shape
case object Triangle extends Shape

Three case object declarations — Circle, Square, Triangle — are added, each extending Shape.

Convert var to val

catalog.scala's Main class declares items with var, though nothing in the class reassigns it.

$ act refactor-lang convert_var_to_val --file catalog.scala --params '{"line":2,"column":3}'

Before

class Main {
  var items = List(1, 2, 3)
}

After

class Main {
  val items = List(1, 2, 3)
}

var becomes val; the initializer List(1, 2, 3) is untouched.

Implement a sealed subclass

tree.scala declares sealed abstract class Tree with one existing subclass, case class Branch(left: Tree, right: Tree) extends Tree.

$ act refactor-lang implement_sealed_subclass --file tree.scala --params '{"subclass_name":"Leaf","fields":"value: Int","line":1,"column":1}'

Before

sealed abstract class Tree
case class Branch(left: Tree, right: Tree) extends Tree

After

sealed abstract class Tree
case class Leaf(value: Int) extends Tree
case class Branch(left: Tree, right: Tree) extends Tree

A new case class Leaf(value: Int) extends Tree is inserted above Branch; Branch's own declaration is untouched.

Convert an if/else to a match expression

classify.scala's classify method returns one of two string literals from an if/else.

$ act refactor-lang convert_ifelse_to_match --file classify.scala --params '{"match_expr":"x","line":3,"column":5}'

Before

object Main {
  def classify(x: Int): String = {
    if (x > 0) {
      "positive"
    } else {
      "negative"
    }
  }
}

After

object Main {
  def classify(x: Int): String = {
    x match {
      case x > 0 => "positive"
      case _ => "negative"
    }
  }
}

The if (x > 0) … else … becomes x match { … }, with the positive branch as case x > 0 and the else branch as case _.

Query

18 query tools, the same on every supported language. Descriptions live in the shared reference: /docs/query-tools.

callers control_flow data_flow definition diagnostics effect_closure effect_summary fix_auto get_type graph import_organize interface mutations references repo_outline skeleton symbols symbols_batch

Refactor

Analysis

42 analysis tools, the same on every supported language. Descriptions live in the shared reference: /docs/analysis-tools.

analyze_api_diff analyze_chokepoints analyze_clones analyze_clusters analyze_cohesion analyze_conformance analyze_coupling analyze_cycle_risk analyze_cycles analyze_dead_code analyze_depth analyze_entry_points analyze_export analyze_extraction analyze_fan_balance analyze_features analyze_hotspots analyze_impact analyze_inconsistencies analyze_inheritance analyze_interface_bloat analyze_interfaces analyze_layers analyze_orphan_types analyze_patterns analyze_platform_deps analyze_readiness analyze_roles analyze_seams analyze_stability analyze_surface analyze_test_gaps analyze_thickness analyze_type_completeness churn_hotspots co_change_clusters coverage_overlay ownership_map profile_overlay simulate split_module trace_overlay

Verify

14 verify tools, the same on every supported language. Descriptions live in the shared reference: /docs/verification.

bisect_regression gate generate_test_harness scan secret_surface summarize_pr taint_flow unsafe_surface verify_behavioral_equivalence verify_contract_preserved verify_diff_semantics verify_port_parity verify_side_effects verify_test_impact