Connect Claude Code to the thirds.ai MCP server

You add thirds.ai to Claude Code as a remote MCP server with one claude mcp add command and your thirds.ai API key. After that, you can ask Claude Code for an invoice, a report, or a post image, and it makes the file from one of your saved designs. thirds.ai lets you save a design once with your logo, colours, and fonts, then type in new details and get a finished PDF or image. You stop rebuilding the same layout by hand, and every file looks like your brand. Each finished PDF or image costs one credit, and a verified free account gets 50 credits a month.

You can also install the thirds.ai plugin instead. It adds the same server and every thirds.ai skill, and you sign in with your thirds.ai account, so you don't need a key.

See the Claude image examples for designs and prompts to try after setup. If you build your app in Replit instead, the Replit MCP setup connects Replit Agent to the same saved designs. If you build in Lovable, the Lovable MCP setup adds them to Lovable chat.

Make it without code

You can make the same PDFs and images in the thirds.ai editor without Claude Code or any setup. It takes three steps, and all you need is a free thirds.ai account. The Release notes template is a good first try if you ship software, because you fill it in again for every version.

1. Open the Release notes template and click Use this template. Sign in and verify your account first if you need to.
2. Open the Data tab and type your product name, the version, and each change. Click Add row for another change. Then click Preview with data above the canvas to check the page. The preview is free.
3. Click Export, then Save and export PDF, and download the file.

When you'd rather have Claude Code fill in the same design from your changelog, connect it to the thirds.ai MCP server.

Add the thirds.ai MCP server to Claude Code

You add the thirds.ai MCP server to Claude Code with one terminal command that names the server URL and sends your API key as a bearer token. It takes two steps. You need Claude Code installed and a key from the API keys page.

1. Save the key as THIRDS_API_KEY in your shell profile or secret store.
2. Run this command in your terminal, not inside a Claude Code session:

claude mcp add --transport http --scope user thirds https://thirds.ai/mcp \
  --header 'Authorization: Bearer ${THIRDS_API_KEY}'

The single quotes keep the key out of the command and the saved configuration. Claude Code reads ${THIRDS_API_KEY} from your environment each time it connects. The user scope makes the server available in all of your projects. Claude Code supports remote HTTP servers and environment variables in headers, as the Claude Code MCP guide describes (checked 25 September 2026). If you run Claude Code inside Zed, Zed can also pass the thirds.ai MCP server you add in Zed to Claude Code.

Add the thirds.ai plugin to Claude Code

You add the thirds.ai plugin to Claude Code with two commands inside a Claude Code session. The plugin comes from the public thirds.ai skills repository. It adds every thirds.ai skill and connects Claude Code to https://thirds.ai/mcp. Claude Code documents plugins and marketplaces in its plugin guide (checked 30 September 2026).

1. Add the thirds.ai marketplace:

/plugin marketplace add thirdsai/skills

2. Install the plugin:

/plugin install thirds-ai@thirds-ai

3. The first time Claude Code uses thirds.ai, sign in to your thirds.ai account in the browser page that opens. If no page opens, type /mcp, pick the thirds.ai server, and choose to sign in.

A plugin sign-in can't make AI pictures, because only an API key connection can. Use the plugin or the claude mcp add command, not both, so Claude Code doesn't list thirds.ai twice.

Which Claude Code scope should you use?

For thirds.ai, user scope suits most people, because Claude Code then loads the thirds.ai server in every project and keeps it private to you. Claude Code has three scopes, and they differ in where the server is saved and who gets it. Project scope suits a team that wants one shared server definition in its repository.

This table follows the Claude Code MCP quickstart (checked 25 September 2026). To share the server with your team, run the command with --scope project, or add this entry to a project .mcp.json file:

{
  "mcpServers": {
    "thirds": {
      "type": "http",
      "url": "https://thirds.ai/mcp",
      "headers": {
        "Authorization": "Bearer ${THIRDS_API_KEY}"
      }
    }
  }
}

Keep THIRDS_API_KEY out of the JSON file and source control. Each person sets their own key. Claude Code asks each person to approve a project server the first time they run claude in that project.

Check the connection

You check the thirds.ai connection with claude mcp list in your terminal or /mcp inside Claude Code, and the thirds server must show as connected. Neither check spends credits. Run claude mcp get thirds to see the saved settings and any error.

These status names come from the Claude Code MCP quickstart (checked 25 September 2026).

Make your first file from Claude Code

Your first thirds.ai file from Claude Code takes three prompts, and you approve the credit before anything is made. You need a connected server and at least one credit. If you saved the Release notes template in the editor, Claude Code can find it in your saved templates.

1. Ask Claude: "List the thirds.ai tools and my saved templates." Listing is free.
2. Ask for the file: "Use my thirds.ai Release notes template to make a PDF for version 2.1 from CHANGELOG.md. Show me the tool call and the credit cost first."
3. Approve the call. Claude Code may ask for permission the first time it uses a thirds.ai tool. Claude then checks the status until the PDF is ready and gives you a download link. Download the file before the link expires.

Read the main MCP guide before your first paid call. It explains credit approval, idempotency keys, status checks, and private content. When you want Claude Code to follow a full file task, choose a guide from the agent skills library. If you also work in Warp, you can connect Warp to the same thirds.ai server or let Warp load the one you added to Claude Code.

FAQ

Why does the server show as failed?

Check that THIRDS_API_KEY is set in the environment that starts Claude Code. Then check that the key is active and the URL is exactly https://thirds.ai/mcp.

Can I give the key variable any name?

Almost any name works, and THIRDS_API_KEY is a safe choice. Claude Code reads some credential names as empty in a remote server's headers, such as ANTHROPIC_API_KEY and NPM_TOKEN, so the server gets no key and answers 401. THIRDS_API_KEY isn't one of those names, according to the Claude Code MCP guide (checked 25 September 2026).

Can I share this setup with my team?

Yes. Use project scope or commit the .mcp.json file. Each person must set their own THIRDS_API_KEY. Never commit a key. If some of your team works in VS Code, they can add the thirds.ai MCP server to VS Code with a shared .vscode/mcp.json file that asks each person for their own key. Teammates who use OpenCode can share a project opencode.json in the same way, as the OpenCode MCP config guide shows.

Does connecting spend credits?

No. Connecting and listing tools don't spend credits. AI template work and successful files can. Ask your agent to show the action and the cost before it starts paid work.