Crystal — 133 Operations for AI Agents

This page is the canonical reference an AI coding agent uses to refactor, query, and analyze Crystal code through the act MCP server. 133 operations available: 59 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
59Refactor
42Analysis
14Verify

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-generic-type-parameter Add a type parameter to a class definition
add-guard-clause Add a guard clause (early return) at the beginning of a method body
add-missing-require Add missing require statement for a used dependency
add-nil-guard Add nil guard check before dereferencing a potentially nil value
add-type-restriction Add type restriction to a method parameter or variable
add-visibility-modifier Add visibility modifier (private/protected) to a method
consolidate-require-statements Consolidate duplicate or redundant require statements
convert-case-to-if Convert case expression to if-elsif chain
convert-class-to-struct Convert class definition to struct definition
convert-if-to-case Convert if-elsif chain to case expression
convert-lambda-to-proc Convert lambda literal to Proc.new block
convert-proc-to-lambda Convert Proc.new block to lambda literal
convert-struct-to-class Convert struct definition to class definition
convert-to-safe-navigation Convert nil-check + method call pattern to safe navigation operator &.
convert-to-string-interpolation Convert string concatenation to string interpolation
convert-to-try Convert begin/rescue block returning nil to inline rescue nil
convert-to-union-type Convert a type annotation to a union type by adding a new type
extract-constant Extract expression into a new constant
extract-method Extract code block into a new method with parameter inference
extract-variable Extract expression into a new local 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)]
generate-abstract-method-stub Generate stub implementation for an abstract method
generate-constructor Generate initialize constructor from instance variables
generate-equality-operator Generate == equality operator for a class
generate-getter Generate getter method for an instance variable
generate-interface-methods Generate method stubs required by an included module interface
generate-method-stub Generate method stub with raise NotImplementedError
generate-null-check Generate a nil check guard for a variable before a given line
generate-property Generate property (getter + setter) for an instance variable
generate-setter Generate setter method for an instance variable
generate-spec-scaffold Generate spec scaffold for a class or method
generate-to-s-method Generate to_s method for a class
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-method Replace method call with method body
inline-variable Replace variable reference with its value
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-constant Introduce a new constant for an expression
introduce-parameter Introduce a new parameter for an expression
introduce-variable Introduce a new local variable for an expression
invert-if-condition Invert if condition and swap then/else branches
move-to-new-file Move class, module, or method to a new 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)]
qualify-name-with-module Qualify an unqualified name with its module prefix
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-nil-check Remove redundant nil check
remove-type-restriction Remove type restriction from a method parameter or variable
remove-unused-parameter Remove a parameter from a method signature that is not used in the body
remove-unused-require Remove require statement for an unused dependency
remove-unused-variable Remove a variable assignment where the variable is never read afterward
remove-visibility-modifier Remove visibility modifier from a method
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-class Rename class and update all references
rename-constant Rename constant and update all references
rename-identifier Rename variable, parameter, method, or constant across all references
rename-method Rename method and update all call sites
rename-module Rename module and update all references
simplify-boolean-expression Simplify a boolean expression using logical laws
simplify-string-concatenation Simplify chained string concatenation into a single expression

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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