Justonce Plugin

JustOnce is a persistent memory layer for AI coding assistants, delivered over MCP. Tell it your stack, conventions, project decisions and preferences once and every tool you use — Cursor, Claude, ChatGPT, VS Code, Claude Code and any other MCP client — recalls them in every later session, with a full bitemporal history of what was true and when.

It does three things:

• Memories — facts, decisions and preferences the assistant stores and recalls across sessions and tools (add_memory, search_memories, get_context).
• Documents — specs, READMEs, config and PDFs stored alongside memories so the assistant can fetch them back into context when needed (store_document, fetch_document).
• Shared spaces — a team or a client engagement shares memories, and every member's own assistant can use them. Owner, editor and viewer roles control who can change what (open_shared_space, share_memories).

It is one vault, not one per app: the same memory follows you across assistants, and through shared spaces it follows your team, clients and contractors too — each with their own assistant, each seeing only what was shared with them.

This repository is the public MCP plugin manifest for the hosted JustOnce server. The server itself runs at https://mcp.justonce.ai/. There is nothing to build or self-host: install the plugin, sign in, done.

• Website & setup guide: https://justonce.ai/connect
• Privacy policy: https://justonce.ai/privacy
• Terms: https://justonce.ai/terms
• Support: https://justonce.ai/contact

Install

Client	How
Cursor	Add to Cursor — or paste the JSON below into ~/.cursor/mcp.json
Claude.ai / Claude Desktop	Settings → Connectors → Add custom connector → URL https://mcp.justonce.ai/
Claude Code	claude mcp add --transport http justonce https://mcp.justonce.ai/
ChatGPT	Settings → Connectors → Create → URL https://mcp.justonce.ai/
VS Code / GitHub Copilot	Add the JSON below to .vscode/mcp.json (use "servers" instead of "mcpServers")
Any other MCP client	Streamable HTTP endpoint https://mcp.justonce.ai/

{
  "mcpServers": {
    "justonce": {
      "type": "streamable-http",
      "url": "https://mcp.justonce.ai/"
    }
  }
}

Authentication

JustOnce uses OAuth 2.0 with PKCE and dynamic client registration. No API key or token goes in any config file. The first time a client connects it opens a browser window where you sign in to (or create) your JustOnce account and approve the scopes; the client stores the resulting token itself.

Discovery endpoints, for clients that need them:

• https://mcp.justonce.ai/.well-known/oauth-protected-resource
• https://mcp.justonce.ai/.well-known/oauth-authorization-server

Scopes: memories:read, memories:write, context:read, categories:read.

What the assistant gets

Once connected, the assistant can:

• Remember — add_memory, update_memory, forget_memory, import_memories
• Recall — search_memories, get_context, get_core_profile, get_memory
• Travel in time — get_as_of, get_memory_history (bitemporal: what was true, and when you knew it)
• Walk the graph — get_relationships (flat edges, or a multi-hop walk with depth), find_related_entities (list entities, or verify one value with name)
• Files & documents — store_document, fetch_document, request_upload_link
• Shared spaces — list_shared_spaces, open_shared_space, close_shared_space, list_space_memories, share_memories (action share / unshare)

Every tool carries readOnlyHint / destructiveHint annotations so clients can ask before anything is changed or erased. forget_memory is permanent.

Shared spaces — a memory layer you can share

Your personal vault is private and is never shared. A shared space is a separate container you choose to put specific memories and documents into, and invite people to:

• One space per relationship. A team space, a space per client or engagement, a space per open-source project. Separate spaces mean separate memberships — no cross-client bleed, no over-sharing.
• Three roles, nothing to configure. Owner, Editor and Viewer.
• Works across assistants. Members connect whichever MCP client they like. When someone asks their assistant a question, search_memories also returns hits from the shared spaces they belong to, each carrying a shared block that says which space it came from and who shared it — so the assistant attributes it correctly instead of presenting it as the user's own.
• Roles decide who edits. Owners and Editors can change a shared memory; Viewers can only read it. Remove a memory from a space, or close the space, and it stops being visible to the other members.

Typical uses: a team giving every member's AI the same architecture decisions, conventions and runbooks; a contractor or agency holding a client's stack and preferences in a space that is closed when the engagement ends; a maintainer sharing project context with contributors without exposing anything personal.

Data & privacy

Memories are encrypted at rest and belong to the signed-in user only. JustOnce never trains on your data. Full details: https://justonce.ai/privacy.

About this repo

This repo follows the Agent Plugins standard (plugin.json + mcp.json) and also ships a Cursor-native manifest in .cursor-plugin/. It contains no server code — the JustOnce service is proprietary and hosted by Bluesoul Technology.

Found a problem with the manifest or docs? Open an issue here. Product support: https://justonce.ai/contact.