# Context Engine

> A multi-tenant context engine: durable memory over an organisation's notes,
> records, files and conversations, searchable by an agent over MCP. Each
> engine is one tenant, with its own database, vector index and credential.

This file is for an LLM or an agent evaluating whether to use Context Engine.
Every link below is served without a credential.

## Start here

- [MCP endpoint](https://pr-278.cntxtngn.com/mcp): the tool surface, and the whole product. Needs
  a token — either an engine's API key as a bearer credential, or an OAuth 2.1
  access token. It answers 401 without one, and the 401 names the document
  below.
- [Protected resource metadata](https://pr-278.cntxtngn.com/.well-known/oauth-protected-resource):
  RFC 9728, which is what an MCP client reads after that 401.
- [Authorization server metadata](https://pr-278.cntxtngn.com/.well-known/oauth-authorization-server):
  RFC 8414. It carries the authorization, token and registration endpoints, so a
  client that has never been heard of here can register itself and obtain a
  token without any of them being written down twice.

## Signing up

You can create an engine in one call, and you do not need an account to do it.
What you cannot do is own one: an engine starts belonging to nobody, and the
person you are acting for becomes its owner by opening a link you hand them.

```
POST https://pr-278.cntxtngn.com/signup/agent
content-type: application/json

{"email": "the-person@example.com", "name": "Their engine"}
```

The reply carries an API key shown once, the MCP endpoint, and a `claim_url`.
Give the claim_url to that person. Until they open it the engine is on a starter
ceiling, and **it is deleted if nobody claims it** — say so when you report back,
or you will leave somebody a link they do not know they need.

A **202** means the engine and key are live but its search index is still
building. Do not call this route again — that makes a second engine. Poll
`status_url` instead, sending the same key, until `status` is `"ready"`:

```http
GET https://pr-278.cntxtngn.com/signup/agent/status
authorization: Bearer <the api_key you were given>
```

- [Sign in or create an account](https://pr-278.cntxtngn.com/login): the way a person does it,
  with no engine created until an address is proved. Never rate limited by the
  agent path above.
- [An account belongs to a person](https://pr-278.cntxtngn.com/help/account.md): an API key names
  an engine and never a person, so a key you are given carries the reach of the
  engine it belongs to and nothing else.

## Free tier

Every engine starts free. The ceilings are enforced rather than advertised — an
answer is refused once either the message count or the spend is reached, and the
calendar month resets both.

- 100 agent messages a month
- $0.50 of model spend, of which up to $0.10 may go on voice
- 2 connected MCP servers
- up to 12 tool steps in one answer

Paid plans, and what an engine has actually spent, are at
[Plans, limits and what an engine spends](https://pr-278.cntxtngn.com/help/billing.md).

## Manual

Every topic below is served as Markdown at the link, and as a page for a person
at the same path without `.md`. [The index](https://pr-278.cntxtngn.com/help/index.json) is the
same set as JSON, with keywords, for choosing one. Content version dc634874c40b.

- [What an engine is](https://pr-278.cntxtngn.com/help/engine.md): One organisation’s own body of knowledge, with its own database and search index.
- [Asking the engine](https://pr-278.cntxtngn.com/help/chat.md): How an answer is put together, and what the assistant can do while answering.
- [Who can read a conversation](https://pr-278.cntxtngn.com/help/visibility.md): Private and team conversations, what private does not cover, and which one each way of starting picks.
- [Finding an earlier conversation](https://pr-278.cntxtngn.com/help/conversations.md): The rail lists the recent ones; the Conversations page lists them all.
- [Finding anything, from anywhere](https://pr-278.cntxtngn.com/help/searching.md): Press ⌘K (Ctrl-K on Windows) to search your records and jump to any page, without leaving what you are doing.
- [Getting a conversation out](https://pr-278.cntxtngn.com/help/export-transcript.md): Export a whole conversation as Markdown — copy it, or download the file — to send to somebody looking into a problem.
- [What the engine holds, and how to point at one thing](https://pr-278.cntxtngn.com/help/records.md): Records, their types, refs like note::retention-policy, and where to browse them.
- [Tasks](https://pr-278.cntxtngn.com/help/tasks.md): Two ways to write one down — the Tasks page or Home — and completing one is a transition, not an edit.
- [Reminders](https://pr-278.cntxtngn.com/help/reminders.md): Ask for one, confirm the draft, and it arrives once by email at the time you named.
- [Attaching and storing files](https://pr-278.cntxtngn.com/help/files.md): Three ways to attach — paperclip, drop, paste — how large they can be, and what the assistant can read of one.
- [Who can sign in to this engine](https://pr-278.cntxtngn.com/help/users.md): Owner, admin and member — and which of them can change the list.
- [Telling it which person you are](https://pr-278.cntxtngn.com/help/profile.md): Set your profile on the Users page and "what have I been in?" starts working. Until then it cannot tell.
- [Adding somebody to this engine](https://pr-278.cntxtngn.com/help/invitations.md): Two ways — the Invitations tab under Users, or ask here and confirm the draft. Only an owner or admin can.
- [Signing in](https://pr-278.cntxtngn.com/help/signing-in.md): No passwords — a mailed link and code, or Google or GitHub, plus an optional second step.
- [Two-step sign-in](https://pr-278.cntxtngn.com/help/two-step.md): Add a code from an authenticator app on top of the emailed one. Optional, and set up under Account → Security.
- [Your account and your name](https://pr-278.cntxtngn.com/help/account.md): Set what people and the assistant call you on the Account page. Your email address is the account and does not change.
- [The engine’s own settings](https://pr-278.cntxtngn.com/help/engine-settings.md): The assistant’s name, tone, backstory and guidance, the engine’s timezone, and voice.
- [Talking and listening](https://pr-278.cntxtngn.com/help/voice.md): Dictate a message, have an answer read aloud; both count against the plan’s voice allowance.
- [Connecting out to another app](https://pr-278.cntxtngn.com/help/connections.md): Outbound — connected app accounts and MCP servers you point it at. See Inbound for the other direction.
- [What can reach in](https://pr-278.cntxtngn.com/help/connections-inbound.md): Inbound — approved applications, and how Claude, claude.ai, ChatGPT, Claude Code and scripts get in.
- [The API key](https://pr-278.cntxtngn.com/help/api-key.md): One key per engine, shown once, in Engine details on Home. Rotating replaces it everywhere it is used.
- [Plans, limits and what an engine spends](https://pr-278.cntxtngn.com/help/billing.md): Three ceilings — messages, spend and voice inside it — reported monthly.
- [More than one engine](https://pr-278.cntxtngn.com/help/engines.md): Switching between engines, and creating another.
- [Sending a message to somebody here](https://pr-278.cntxtngn.com/help/messaging.md): Ask the assistant to tell a colleague something; you see the exact words and press send. Members only.
- [What the assistant cannot do](https://pr-278.cntxtngn.com/help/limits.md): It sends nothing on its own, schedules nothing, keeps nothing after a turn, and reads only what is public.