# The three doors

A house is one MCP server with three routes. Each route serves a profile, and each profile
contains the one before it. The route names are German.

| Door | Route | Skills | What it adds |
|---|---|---|---|
| reader | `/leser` | 42 | finding, describing, reading, walking, counting; writes nothing |
| author | `/autor` | 97 | storing values, creating individuals and documents, asserting and retracting facts, notes, open questions, plans, conversations |
| modeller | `/modellierer` | 100 | the vocabulary: `define_form`, `define_aspect`, `include_concept` |

The numbers are those of the house software as of 2026-10-01. The root of the address serves the
reader profile.

Doors are not tiers and not licences. They are a way to give an agent exactly the reach
its job needs: a reviewing agent connects to the reader door and cannot write, however it
is prompted. The reader door does not know the writing skills at all: calling `store_text`
there is answered with "unknown tool".

## The house describes its own skills

- `list_skills` returns every skill with the smallest door that serves it, whether it
  writes, whether repeating a call is harmless, and one sentence of summary.
- `read_skill` returns one skill whole: the full description and the parameter schema
  exactly as the door serves it. A skill that needs a higher door says so: `define_form`
  read through the reader door carries the hint that it is callable from the modeller
  profile upwards.

Read a skill before you use it the first time. The descriptions state conventions that a
name cannot: that creating never searches, that a path is an array, that a year is a span.
`read_skill` shows the arguments of a skill, not the shape of its answer; look at the first
answer before you script against it.

## Preambles

Each door greets a connecting agent with a short instruction. The modeller door's says:
call `overview` first; reuse before coinage; every answer reports `is_new`, and that is
your accountability. The word varies in practice: storing and asserting skills report
`is_new`, creating skills `created`, and `set_property` reports `changed`.

## Errors are written for you

Where the house refuses, it says what would work. Asking for the versions of a document
without naming the aspect was answered:

> No property slot 'Structure' at this thing. No property slot here without a context.
> Also at this thing: Structure — pass context_id '…' (Document).

One exception found while writing this manual: an argument of the wrong JSON type (a
string where an array is expected) is answered with a bare "an error occurred" and no
hint. If you get that, compare your arguments with the schema from `read_skill`.

## Besides the doors

- `GET /binary/{hash}` and `POST /binary` carry bytes. They carry no meaning: an upload
  returns a content hash, and a skill gives the hash its meaning.
- `/ops` is the operations endpoint: it reports the state of the service, not the content
  of the house.

## Who may connect

A house today listens on its own machine only and has no keys. Access from outside, with a
key per person, is planned and is a precondition for houses on VMs.

## Go deeper

- [first-hour-in-a-house](first-hour-in-a-house.md): the doors in use
- [forms-aspects-concepts](forms-aspects-concepts.md): the modeller door
- [finding-things](finding-things.md): the reader door
- [a-memory-you-can-shape](a-memory-you-can-shape.md)