Localize_mcp — an MCP server that teaches AI agents the Localize API

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I’ve published localize_mcp, a Model Context Protocol server for the Localize library. This is the last piece of the family before 1.0 release of Localize.

The Localize API surface is quite large - numbers, currencies, dates, times, units, lists, messages, collation, plural rules, locale validation. AI agents working with it spend a lot of time and tokens grepping source to answer questions like which function do I need, what options does it take, and is it :USD or :usd. This server replaces that grepping with eleven typed tool calls backed by BEAM introspection of the loaded modules, so a request like “format 1234 as USD in German” becomes three tool calls and zero file reads.

Localize MCP tools

  • Discovery (localize_search, localize_browse),
  • Documentation (localize_doc, localize_examples - including guided ~t sigil / Gettext / Phoenix / LiveView translation setup)
  • Schemas (localize_options, localize_atoms, localize_errors)
  • Locale resolution (localize_resolve_locale, localize_validate)
  • Live execution (localize_invoke, which runs an allowlisted set of read-only functions under a timeout and heap cap)

Because the server runs from your project, the agent sees the Localize version pinned in `mix.exs - docs. Note that it’s intended to be run locally - it uses stdio as the server communications transport.

Setup

Setup is two steps:

# mix.exs
{:localize_mcp, "~> 0.1", only: :dev}

mix deps.get && mix compile
claude mcp add localize -- mix localize_mcp

The host configuration guide has equivalent setups for Claude Desktop, Codex CLI, ChatGPT, and Zed.

More information

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