TypeScript — 164 Operations for AI Agents

This page is the canonical reference an AI coding agent uses to refactor, query, and analyze TypeScript code through the act MCP server. 164 operations available: 90 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.

18Query

90Refactor

42Analysis

14Verify

Worked TypeScript examples

act101 treats the TypeScript type layer as a refactoring surface, not just a checker: the engine can derive a runtime type guard from a static interface, collapse an enum into a string-literal union, or rewrite an interface as a type alias — every edit resolved against the syntax tree, never by text search. Each example below is the verbatim output of the command shown, run against the file shown.

Derive a runtime type guard from an interface

A webhook handler receives `unknown` JSON and needs a runtime check that mirrors the static `WebhookEvent` shape.

$ act refactor generate-type-guard --file webhooks.ts --name WebhookEvent

Before

export interface WebhookEvent {
  id: string;
  kind: string;
  payload: Record<string, unknown>;
  receivedAt: string;
}

After

export interface WebhookEvent {
  id: string;
  kind: string;
  payload: Record<string, unknown>;
  receivedAt: string;
}

function isWebhookEvent(value: unknown): value is WebhookEvent {
    return (
        typeof value === 'object' &&
        value !== null &&
        typeof (value as WebhookEvent).id === 'string' &&
        typeof (value as WebhookEvent).kind === 'string' &&
        typeof (value as WebhookEvent).payload === 'object' && (value as WebhookEvent).payload !== null &&
        typeof (value as WebhookEvent).receivedAt === 'string'
    );
}

The generated `isWebhookEvent` narrows `unknown` to `WebhookEvent`, property by property, including the null guard on the `Record` field.

Collapse an enum into a string-literal union

`EventKind` only ever carried string payloads; the union form is lighter and erases nothing at the serialization boundary.

$ act refactor convert-enum-to-union EventKind

Before

export enum EventKind {
  PaymentSucceeded = "payment.succeeded",
  PaymentFailed = "payment.failed",
  RefundIssued = "refund.issued",
}

After

export type EventKind = "payment.succeeded" | "payment.failed" | "refund.issued";

The five-line enum becomes one union type. The member values survive verbatim, so already-serialized data keeps parsing.

Rewrite an interface as a type alias

House style prefers `type` aliases for object shapes that are never merged or extended.

$ act refactor convert-interface-to-type FeatureFlag

Before

export interface FeatureFlag {
  key: string;
  enabled: boolean;
  rolloutPercent: number;
}

After

export type FeatureFlag = {
  key: string;
  enabled: boolean;
  rolloutPercent: number;
};

Only the declaration form changes — the three members, their types, and the `export` survive untouched.

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

Operation	Description
`add-barrel-export`	Add barrel export for module
`add-discriminant`	Add discriminant property to union type
`add-nullish-coalescing`	Add nullish coalescing operator
`add-numeric-separators`	Add numeric separators to large numbers
`add-optional-chaining`	Add optional chaining operator
`add-readonly`	Add readonly modifier to property
`add-satisfies`	Add satisfies type constraint
`add-type-annotation`	Add type annotation to variable or parameter
`add-type-import`	Convert import to type-only import
`change-signature`	Change function signature
`change-type`	Change variable/parameter type
`change-visibility`	Change member visibility
`convert-arrow`	Convert function to arrow function
`convert-async`	Convert between async/sync
`convert-callback-to-promise`	Convert callback pattern to Promise
`convert-class-to-function`	Convert class to function
`convert-commonjs-to-esm`	Convert CommonJS to ES modules
`convert-concat`	Convert array concatenation methods
`convert-const-to-let`	Convert const to let
`convert-const-to-var`	Convert const to var
`convert-enum-to-union`	Convert enum to union type
`convert-esm-to-commonjs`	Convert ES modules to CommonJS
`convert-for`	Convert between for loop variants
`convert-foreach`	Convert for loop to forEach
`convert-if-else`	Convert between if-else and ternary
`convert-interface-to-type`	Convert interface to type alias
`convert-namespace-to-module`	Convert namespace to module
`convert-promise-chain-to-async`	Convert promise chain to async/await
`convert-prototype-to-class`	Convert prototype pattern to ES6 class
`convert-require-to-import`	Convert require() to import
`convert-sync`	Convert async function to sync
`convert-template`	Convert string concatenation to template literals
`convert-ternary`	Convert ternary to if-else
`convert-type-to-interface`	Convert type alias to interface
`convert-union-to-enum`	Convert union type to enum
`convert-var-to-block-scope`	Convert var to block-scoped declaration
`convert-var-to-const`	Convert var to const
`convert-var-to-let`	Convert var to let
`encapsulate`	Encapsulate field with accessors
`extract-class`	Extract methods/fields to new class
`extract-constant`	Extract value to named constant
`extract-enum-member`	Extract enum member to separate enum
`extract-function`	Extract code into a new function
`extract-interface`	Create interface from class
`extract-method`	Extract code into a new class method
`extract-type`	Extract inline type to type alias
`extract-variable`	Extract expression to variable
`extract_function`	Extract a code selection into a new function — automatically infers parameters, return types, and inserts the call site. Use instead of manually cutting/pasting code. Works without LSP; LSP improves type inference. Params: file (string), new_name (string), start_line (u32), start_column (u32), end_line (u32), end_column (u32) [, preview (bool), receipt (bool)]
`extract_variable`	Extract an expression into a named variable — inserts the declaration and replaces the expression with the variable name. Works without LSP. Params: file (string), new_name (string), start_line (u32), start_column (u32), end_line (u32), end_column (u32) [, preview (bool)]
`flatten`	Flatten nested structure
`generate-accessors`	Generate getters/setters for fields
`generate-builder`	Generate builder pattern
`generate-constructor`	Generate constructor from fields
`generate-equals`	Generate equals method
`generate-from-json`	Generate fromJSON static method
`generate-hash`	Generate hashCode method
`generate-impl`	Generate interface implementation stubs
`generate-mapped-type`	Generate mapped type from interface
`generate-tests`	Generate unit tests
`generate-to-json`	Generate toJSON method
`generate-to-string`	Generate toString method
`generate-type-guard`	Generate type guard function
`import-add`	Add import statement
`import-alias`	Add or change import alias
`import-organize`	Organize import statements
`import-remove`	Remove import statement
`inline`	Inline a variable, function, or method — replace every usage with its definition body, then remove the original. The inverse of extract. Works without LSP (single-file); LSP enables cross-file inlining. Params: file (string), symbol (string) [, line (u32), preview (bool), receipt (bool)]
`inline`	Inline variable or function
`insert_body`	Replace a function's implementation body with new code. AST-validated — rejects if the result has parse errors, so you can't accidentally break syntax. Use instead of manual text editing for function rewrites. Params: file (string), symbol (string), code (string) [, commit (bool)]
`introduce-field`	Introduce new field
`introduce-parameter`	Introduce new parameter
`introduce-variable`	Introduce new variable
`move`	Move symbol to another file
`move_symbol`	Move a function, class, or type to a different file and automatically update all imports across the codebase. Use instead of manually cut/paste + fixing imports. Works without LSP (single-file); LSP enables cross-file import updates. Params: file (string), symbol (string), destination (string) [, preview (bool), receipt (bool)]
`recipe_run`	Run a codemod recipe: declarative match → transform → optional verify across modeled grammars. Preview lists matches; apply writes with optional E7 receipts and all-or-nothing rollback. Returns a per-site report.
`remove-type-annotation`	Remove inferred type annotation
`remove-type-assertion`	Remove unnecessary type assertion
`rename`	Rename a symbol and automatically update ALL references across the codebase. Safer and faster than find-and-replace — AST-aware, won't rename strings or comments. Works without LSP (single-file); LSP enables cross-file renames. Params: file (string), old_name (string), new_name (string) [, line (u32), column (u32), preview (bool), receipt (bool)]
`rename`	Rename symbol and all references
`use-destructuring`	Use destructuring for assignments
`use-logical-assignment`	Use logical assignment operators
`use-object-shorthand`	Use object property shorthand
`use-private-fields`	Use private class fields
`use-rest-parameters`	Use rest parameters instead of arguments
`use-spread-operator`	Use spread operator for arrays/objects
`use-template-literals`	Use template literals for string interpolation
`wrap-if`	Wrap in if statement
`wrap-null-check`	Wrap in null check guard
`wrap-optional`	Wrap in Optional/Option/Maybe
`wrap-try-catch`	Wrap in try-catch block

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

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