xcstrings-mcp

MCP server for iOS/macOS .xcstrings localization file management.

The Problem

Xcode String Catalogs (.xcstrings) are large JSON files that waste LLM context windows when loaded whole. Manual editing risks corrupting Xcode's specific formatting, there's no validation for format specifiers or plural rules, and plural-aware translation requires understanding CLDR categories across 40+ locales.

Quick Start

Install

brew install Murzav/tap/xcstrings-mcp
# or
cargo install xcstrings-mcp
# or
cargo binstall xcstrings-mcp

Configure Claude Code

claude mcp add xcstrings-mcp -- xcstrings-mcp

Usage

Typical workflow:

Parse the .xcstrings file to cache it
Get untranslated strings in batches that fit the context window
Submit translations with automatic validation and atomic writes

parse_xcstrings → get_untranslated → submit_translations

Multi-file projects: parse each file — the server caches all of them and tracks the active one. Use list_files to see cached files.

Tools

Tool	Description
`parse_xcstrings`	Parse and cache `.xcstrings` file
`get_untranslated`	Get untranslated strings with batching
`submit_translations`	Validate and write translations atomically
`get_coverage`	Per-locale coverage statistics
`get_stale`	Find stale/removed keys
`validate_translations`	File-wide validation report
`list_locales`	List locales with stats
`add_locale`	Add new locale with empty translations
`remove_locale`	Remove a locale from all entries
`get_plurals`	Extract keys needing plural translation
`get_context`	Find related keys by shared prefix
`list_files`	List all cached files with active status
`get_diff`	Compare cached vs on-disk file (added/removed/modified keys)
`get_glossary`	Get translation glossary entries for a locale pair
`update_glossary`	Add or update glossary terms
`export_xliff`	Export to XLIFF 1.2 for external translation tools
`import_xliff`	Import translations from XLIFF 1.2 file

Prompts

Prompt	Description
`translate_batch`	Step-by-step instructions for batch translation
`review_translations`	Instructions for quality review of translations
`full_translate`	Complete workflow for translating an entire file

CLI Options

xcstrings-mcp --glossary-path ./my-glossary.json

Flag	Default	Description
`--glossary-path`	`glossary.json`	Path to glossary file for consistent terminology

Performance

Binary size: 3.6 MB (stripped + LTO). Zero CPU at idle.

File	Parse	Get untranslated	Validate	RAM
968KB (638 keys × 10 loc)	0.2ms	0.02ms	0.04ms	7.6 MB
4.1MB (2K keys × 10 loc)	24ms	5ms	7ms	40 MB
10.3MB (5K keys × 10 loc)	60ms	11ms	23ms	49 MB
56.7MB (10K keys × 30 loc)	333ms	62ms	221ms	287 MB

Scaling is linear — no degradation cliffs. Typical iOS projects (2-5K keys) parse in under 60ms.

Architecture

┌─────────────┐    stdio/JSON-RPC    ┌─────────────────┐    File I/O    ┌──────────────────────┐
│ Claude Code  │◄───────────────────►│  xcstrings-mcp   │◄────────────►│ Localizable.xcstrings │
│ (translates) │                     │ (Rust MCP server)│              │ (JSON on disk)        │
└─────────────┘                     └─────────────────┘              └──────────────────────┘

Layered architecture: server -> tools -> service -> model, with io injected via the FileStore trait.

server -- MCP tool routing and handler dispatch
tools -- individual tool implementations
service -- pure logic (parser, extractor, merger, validator, formatter); no I/O
model -- serde types for .xcstrings format, CLDR plural rules, format specifiers
io -- FileStore trait + real filesystem implementation with atomic writes

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contributing

See CONTRIBUTING.md for development setup and guidelines.

xcstrings-mcp 0.4.0