Connect Claude to the Minecraft world (Step 4 of 4)

This is the final phase of the Minecraft Java MCP setup. It assumes Phase 3 (setup-server) is done: the mod is running and /healthz returns OK.

Before starting, get from the user:

• The /mcp URL — http://<host>:<port>/mcp, e.g. http://localhost:8765/mcp. Use localhost only if Claude runs on the same machine as Minecraft; otherwise the host's LAN IP or hostname. If the mod uses TLS, the scheme is https.
• The bearer token — only for a dedicated/remote setup (the token captured in Phase 3). A single-player localhost setup has no token.

Name the server minecraft-java. The builder agent and skills in this plugin expect MCP tools under that name (mcp__minecraft-java__*). Use exactly minecraft-java as the server name below.

One or two servers? (world + inspection)

The mod exposes two MCP servers from one jar. Connect whichever match the user's setup:

• minecraft-java — the world server (read/write the world: level_*, block_*, entity_*, …). Runs wherever a Minecraft server runs — a dedicated server, or single-player's integrated server. Default http://localhost:8765/mcp. Always connect this.
• minecraft-java-client — the inspection server: SEE the world the way a player does. view_capture returns the player's actual first-person frame as a PNG; sense_crosshair / sense_raycast / sense_entities / sense_screen / client_status read client-side perception. Runs inside a real, rendered client. Default http://localhost:8766/mcp. Connect this only when a real client is running (see patterns below). Name it exactly minecraft-java-client — exec-inspect looks for mcp__minecraft-java-client__*.

The three supported patterns:

The inspection server is optional: everything builds without it; it adds the real-pixel "what does this look like in-game" check that exec-inspect uses when present (and falls back to the synthetic block_render_region + a user screenshot when absent).

Ask the user which Claude they're connecting: Claude Code (CLI / IDE extension) or Claude Desktop. Follow the matching section.

Connecting Claude Code

The mod speaks the Streamable HTTP transport, which Claude Code supports natively. Use claude mcp add.

Single-player / localhost (no token):

claude mcp add --transport http minecraft-java "http://localhost:8765/mcp"

Add the inspection server when a real client is running (single-player, or a client joined to the server) — see the patterns table above:

claude mcp add --transport http minecraft-java-client "http://localhost:8766/mcp"

For a server+client combo, point each at its own host (the world server on the dedicated host, the inspection server on the client host). Add a matching --header "Authorization: Bearer <token>" if that endpoint requires auth.

Dedicated / remote (with token):

claude mcp add --transport http minecraft-java "http://<host>:8765/mcp" \
  --header "Authorization: Bearer <token>"

Pick a scope with -s: local (default, this project only), project (shared via a committed .mcp.json), or user (all projects on this machine). For a personal setup, user is usually what the user wants: -s user.

Do not commit the token. If the user wants project scope on a remote setup, write .mcp.json with the token pulled from an environment variable instead of inlining it. This plugin ships .mcp.json.example showing that pattern:

{
  "mcpServers": {
    "minecraft-java": {
      "type": "http",
      "url": "${MINECRAFT_MCP_URL:-http://localhost:8765/mcp}",
      "headers": { "Authorization": "Bearer ${MINECRAFT_MCP_TOKEN}" }
    }
  }
}

For localhost single-player, drop the headers block entirely — just the type and url are needed.

After adding it, the user restarts Claude Code (or reloads the window in the IDE extension). Confirm the server shows up with claude mcp list or /mcp — it should report minecraft-java as connected.

Connecting Claude Desktop

Two options:

A — Native custom connector (preferred, if the user's Claude Desktop has it). In Settings → Connectors, add a custom connector with the URL http://<host>:8765/mcp. For a remote setup, add a header Authorization: Bearer <token>; for localhost, no header.

B — Via the mcp-remote adapter. Edit Claude Desktop's config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

Localhost (no token):

{
  "mcpServers": {
    "minecraft-java": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:8765/mcp"]
    }
  }
}

Remote (with token):

{
  "mcpServers": {
    "minecraft-java": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "http://<host>:8765/mcp",
        "--header",
        "Authorization:${AUTH_HEADER}"
      ],
      "env": {
        "AUTH_HEADER": "Bearer <token>"
      }
    }
  }
}

The token goes through the AUTH_HEADER env var so its space (Bearer <space>token) isn't mangled by argument parsing. Then fully restart Claude Desktop — the tools appear under the tools (🔌) menu once it reconnects.

Verify the connection

A registered server isn't a working one — confirm with a live call:

1. Make sure at least one world is loaded (and, ideally, a player is in it — many tools act relative to players or the world).
2. Call server_get_status — it needs no arguments and no player. A successful response (Minecraft version, TPS, online player count, loaded dimensions) means the chain is up: Claude → MCP server (the mod) → world. Then level_get_info with dimension: "minecraft:overworld" confirms world-level reads work.
3. As a visible smoke test, run command_execute with say MCP connected and confirm the user sees the message in the in-game chat.
4. If you connected minecraft-java-client: call client_status — it needs no arguments and confirms the inspection client is in a world (it reports in_game, position, facing). Then view_capture returns the player's first-person frame as an image you can Read. A successful capture means the real-pixel inspection path is live. (If client_status reports in_game: false, the client is on the title screen — join a world and retry.) view_capture defaults to close_screen: true, so it dismisses the pause/Esc menu that opens when you alt-tab and still returns a clean world frame; to stop that menu opening on focus loss at all, toggle Pause on Lost Focus off in-game with F3 + P. The client window must not be minimized (minimized = no rendering = no capture).

If a call fails:

• Auth / 401 — wrong or missing token on a remote setup, or a stray space in the header. (/healthz works without auth, so a 401 on tool calls but a healthy /healthz points squarely at the token.)
• Connection refused / timeout — the mod isn't running (no world loaded / server down), wrong host:port, or a firewall between Claude and the host.
• Tools connect but calls error about no world / no player — load a world and have a player join, then retry.
• Player cannot join a 26.3 dedicated server — 26.3 defaults to white-list=true in server.properties. Set it to false on a private server, or run whitelist add <name> via command_execute. The MCP console tools are unaffected.

Wrap up

Once server_get_status returns cleanly, the setup is complete:

• minecraft-java MCP server registered with Claude.
• Java tools (level_*, block_*, entity_*, …) visible.
• A live test call succeeded against the world.
• (if a client is running) minecraft-java-client registered; client_status and view_capture succeeded — Claude can SEE the world as a player.

Tell the user they're done — all four phases are complete. Suggest next steps:

• Try a simple prompt: "What's the time and weather? Set it to clear midday."
• Try building: "Build a small stone-brick house near the nearest player." Claude works through the Java MCP tools to plan and place blocks in the world.