Hidden Door launches MCP server so AI agents can build and edit story worlds

What the MCP server does

According to Hidden Door, all experiences on its platform run on a narrative world model, described as a rich representation of a world, its characters and places, and its tropes and stories. Creators have built worlds in Atlas Studio for some time. The company is now offering that same set of tools over MCP (Model Context Protocol), which it says extends and complements the editor.

The company groups the features into four areas:

• Create: start from a simple idea such as "a haunted railway," iterate with an agent, view a preview, and approve it so the draft is built.
• Adapt: bring in existing writing, from a page of setting notes to a full manuscript in plain text, and see it turned into characters, locations and items.
• Explore: ask questions about a world, take a guided tour, or learn what a particular dial in Atlas does.
• Adjust: tweak tone, update a character, set a custom portrait, or request a larger thematic change.

For large changes, Hidden Door says the system works out which specific details need to follow, shows the user a plan, and saves it once the user agrees. The company's examples include recasting Pride and Prejudice as a modern rom com or turning a cosy cute animal world into an epic fantasy.

A demonstration with Sleepy Hollow

In the announcement, the author describes importing a plaintext copy of The Legend of Sleepy Hollow from Project Gutenberg, since the book is public domain. According to the post, the agent automatically extracted the expected locations, themes and storylines. Characters were created and given initial art from Hidden Door's avatar library.

The author then asked the agent to find a portrait in a more fitting style and replace one avatar, choosing an Edwin Austin Abbey portrait of Ichabod Crane from Wikimedia Commons. To add a new story, the author used a 1952 comic strip from Adventures Into Darkness, Romance of Death, as inspiration. After a short conversation with the agent, the strip became a horror mystery storyline set in the world. The post says the Tappan Zee shore is already a canon location, a few miles from Sleepy Hollow, and that the storyline follows the comic's beats but lets the player survive depending on how their story goes. All of it can be inspected and edited.

Agents can also move content out of Hidden Door. The company says it has recently been adapting worlds into screenplays for vertical drama and graphic novel formats, and the post mentions turning a storyline into a script or a comic strip into a storyline.

Ground rules and limits

Hidden Door states that the MCP server works on drafts. Agents save them to the user's Hidden Door account, but they do not publish worlds or start games. Playing and sharing happen in Atlas on hiddendoor.co. Deleting a character, location or storyline requires the user's approval first. Behind the scenes, the agent uses a set of Hidden Door skills written by the company, so users describe what they want and the agent operates the controls.

The company also notes that the agent sends the user's writing and requested edits to Hidden Door, where drafts are stored.

How to get started

Use requires a Hidden Door account on a Creator plan. On first connection, the agent prompts the user to sign in to Hidden Door in a browser. The company's plugin installs both the MCP connection and the skills.

• Claude Code: run claude plugin marketplace add HiddenDoor/plugins, then claude plugin install hiddendoor. Start a new session or run /reload-plugins, then sign in when prompted.
• Codex: run codex plugin marketplace add hiddendoor/plugins, then codex plugin add hiddendoor@hiddendoor.
• Other agents: connect to the MCP server at https://www.hiddendoor.co/mcp. Setup instructions are at hiddendoor.co/mcp, and the skills are in the company's GitHub repo.

For creators who already work with an AI agent, the release means world-building in Hidden Door no longer has to start in the editor. The company is asking beta users for feedback and suggests importing works they have the rights to use or adapting them to new genres.