Tidewave Phoenix MCP server

Tidewave Phoenix

Tidewave Phoenix is an MCP server that provides runtime-level tools for developing Phoenix apps using coding agents.

Your agent will be able to use this MCP server to talk to your running Phoenix app in development to:

• execute code in the context of the running app (like an IEx session for agents)
• read the app's live logs
• query your development database
• get source locations of modules and functions
• read documentation pinned to the exact hex package versions your project depends on

This MCP server is an open-source component of Tidewave, the agentic development environment for Phoenix and Rails.

You can use this project as a standalone MCP server or integrated with the Tidewave product by following the installation instructions below.

Installation

1. Add the Tidewave hex package to your app

Option 1: Manually

Add the tidewave package to your mix.exs:

def deps do
  [
    {:tidewave, "~> 0.9", only: :dev},
    {:phoenix, ...},
  ]
end

Then, for Phoenix applications, go to your lib/myappweb/endpoint.ex and right above the if code_reloading? do block, add:

+  if Mix.env() == :dev do
+    plug Tidewave
+  end

   if code_reloading? do

[!TIP]

Tidewave works best with Phoenix LiveView v1.1 or later. Once you update it,

make sure to enable the following options in your config/dev.exs:

elixir

config :phoenixliveview,

debugheexannotations: true,

debug_attributes: true

Those are enabled by default for Phoenix v1.8+ apps.

Option 2: Using Igniter

Alternatively, you can use igniter to automatically install Tidewave MCP into an existing Phoenix application:

# install igniter_new if you haven't already
mix archive.install hex igniter_new

# install tidewave
mix igniter.install tidewave

Umbrella projects

For umbrella projects, you can follow the manual steps above in the application that defines your Phoenix endpoint (typically apps/yourappweb).

2. Add the Tidewave MCP to your agent/editor

Add the Tidewave MCP server to your editor or MCP client configuration as the type "http" (streamable), pointing to the /tidewave/mcp path and port your web application is running at. For example, http://localhost:4000/tidewave/mcp.

We also have specific instructions for:

• Claude Code
• Codex
• Cursor
• Neovim
• OpenCode
• VS Code
• Others

[!TIP]

If you are using worktrees, you are likely running your web server

on different ports, and therefore there isn't a single host and port

combo you can use.

In such cases, you may want to add mix tidewave.proxy as STDIO MCP

instead, which adds a "port" parameter to all tool definitions, and

is responsible to dispatch to the correct application.

Usage

As with any other MCP server, your agent will call the tools exposed by the Tidewave MCP whenever it sees fit. But you can also prompt it to call them explicitly.

Available MCP tools

project_eval

Evaluates Elixir code within your running application, giving the agent access to your runtime, dependencies, and in-memory data. It's like an IEx for the agent.

Your agent can use it when it would rather run code than assume behavior, grounding its next step in what the running app actually does. For example, calling a function to see what comes back or reproducing a failing code path against live app state to debug it.

executesqlquery

Executes a SQL query within your app's development database.

Shortened. The full README is on GitHub.