# MCP Server — Specification

> Written 2026-06-23. Phase 3 of `plan.md`: let claude.ai "cooking mode" read
> and update the pantry directly, so Tom stops reciting his inventory and pantry
> upkeep becomes conversational. Builds on the shipped pantry redesign (the
> `state` field) and auth phase.
>
> Decisions locked in `plan.md §3` and `requirements.md §7`: a **separate
> FastMCP "ai service"** (a pattern Tom already runs elsewhere) that talks to
> the existing Django REST API, hosted on the same box at
> **`food.jihakuz.xyz/mcp`**, behind nginx, **bearer-token** auth.

---

## 1. Goal

One sentence: **Claude, in claude.ai cooking mode, can see what's actually in
the pantry and write changes back — without Tom typing his inventory.**

In scope:
- Read the pantry (what's in / low / out, by location).
- Update item state conversationally ("used the last of the noodles" → Out).
- Add items ("bought eggs and pork mince").
- See what's cookable (the meta-recipe matcher) and the recipe templates
  (which double as a substitution table).
- **Commit ideas back** — create/update a meta-recipe Tom brainstormed in the
  chat, and log a cook (with rating). This is a primary workflow: Tom thinks out
  loud in the LLM, then wants it saved without re-entering it by hand.

Out of scope (for now): the open-ended "this isn't on the shelf, what else
works?" reasoning is *Claude's* job given the recipe/slot data — the MCP just
serves the data; no substitution engine here. Fixed (non-template) recipes stay
admin-managed; the brainstorm→commit path targets meta-recipes.

**Why the cooking blocks still work:** MCP only gives Claude *tools/data*. It
doesn't change how claude.ai renders cooking mode. Claude pulls real pantry
contents through these tools and still produces its normal formatted cooking
blocks — now grounded instead of guessed.

## 2. Architecture

```
  claude.ai (cooking mode)
        │  Streamable HTTP, secret in the URL path
        ▼
  nginx  food.jihakuz.xyz/mcp   (TLS, public)
        │  proxy_pass 127.0.0.1:8765
        ▼
  FastMCP "ai service"  (food-mcp.service, localhost only)
        │  HTTP + DRF token  (the `caine` token)
        ▼
  Django REST API  127.0.0.1:8042/api/   (localhost — bypasses the
        │                                  external /api/ nginx block)
        ▼
  SQLite
```

Three trust hops, three credentials:
- **claude.ai → MCP**: a long random **secret in the connector URL path**
  (see §4). This endpoint is internet-exposed, so that secret is the only thing
  protecting it.
- **MCP → Django API**: the existing `caine` DRF token, over `127.0.0.1` — so
  it reaches Django directly and isn't subject to nginx's external `/api/`
  block.
- **Django → DB**: unchanged.

The MCP service is **inbound-only from claude.ai** and **outbound-only to
localhost Django**. It holds no database connection of its own.

## 3. Transport & hosting

- **Transport:** Streamable HTTP (the remote-MCP transport claude.ai connectors
  use). FastMCP served over HTTP, bound to `127.0.0.1:8765`.
- **Public route:** nginx on `food.jihakuz.xyz`, `location /mcp` →
  `proxy_pass http://127.0.0.1:8765`. TLS via the existing Let's Encrypt setup.
  Note SSE/streaming needs `proxy_buffering off;` and a long
  `proxy_read_timeout` on that location.
- **Process:** its own systemd unit `food-mcp.service` alongside `food.service`,
  runs as `openclaw`, `Restart=on-failure`.

## 4. Auth

**Resolved (checked against Anthropic's connector docs, June 2026):** claude.ai
custom connectors authenticate a remote MCP server one of two ways — **OAuth**
(the server must support Dynamic Client Registration; claude.ai runs the
handshake) or **authless** (no auth). The "Add custom connector" dialog only
asks for the server **URL**; OAuth client id/secret are optional "Advanced
settings". There is **no field to paste a static bearer token or custom
header**, so the original bearer-header plan isn't directly supported. Two ways
to honour the "tight secret, single user" intent:

- **Recommended — authless connector + secret in the URL path.** Register the
  connector URL as `https://food.jihakuz.xyz/mcp/<long-random-secret>/`. To
  claude.ai it's an authless server; in reality nginx proxies *only* that exact
  secret prefix to the FastMCP service and 404s everything else. The URL **is**
  the bearer-equivalent — it matches Tom's "a tight enough secret, I'm the only
  user" call with zero OAuth machinery. Treat the URL as the secret: TLS only,
  keep it out of git, rotate by changing the path.
- **Heavier but properly revocable — OAuth with Dynamic Client Registration.**
  FastMCP can front an OAuth provider. Correct and per-grant revocable, but real
  work for a single-user app. Reach for it only if the URL-secret feels too
  loose.

To confirm first-hand: claude.ai → Settings → Connectors → **Add custom
connector** shows a single URL field (OAuth fields under "Advanced settings").

**MCP → Django** is unchanged: the `caine` DRF token in an `Authorization:
Token …` header, over `127.0.0.1`.

## 5. Tools

Designed for how Claude reasons in conversation — **by ingredient name, not DB
id**. Each maps to the existing API (with the small additions in §6).

| Tool | Purpose | Params | Returns | Backing call |
|---|---|---|---|---|
| `get_pantry` | "What do I have?" | `location?` (fridge/cupboard/freezer), `include_out?` (default false) | items: `{name, state, location, quantity?, unit, expiry?, is_staple}` grouped by location, plus counts | `GET /api/pantry/` |
| `set_item_state` | The conversational update — "used the last of the noodles" | `ingredient` (name), `state` (in/low/out), `location?` | the updated item | **new** `POST /api/pantry/set-state/` (§6) |
| `add_to_pantry` | "I bought eggs and pork mince" | `items: [{name, location?, quantity?, unit?}]` | per-item result (created / restocked) | `POST /api/bulk-pantry-add/` |
| `what_can_i_cook` | Meal options grounded in stock | `servings?` | meta-recipes with `ready/partial/missing` + per-slot availability + expiry warnings | `GET /api/what-can-i-cook/` |
| `get_recipes` | The templates + their slot options (the substitution table) | — | meta-recipes with slots, options, base ingredients | `GET /api/meta-recipes/` |
| `log_cook` | Record a cooked meal + rating — the cook-log commit path | `meta_recipe` or `recipe`, `slot_choices?`, `servings?`, `rating?`, `notes?` | cook-log id + `used_ingredients` (a suggestion set to confirm — **no** auto state change) | `POST /api/log-cook/` (§6) |
| `create_meta_recipe` | Commit a meta-recipe brainstormed in the chat (create or update) | nested template: `name`, `method`, `slots:[{name, options:[{ingredient, qty, unit}]}]`, `base_ingredients:[]` (+ `id` to update) | the saved recipe + any auto-created ingredients | `POST`/`PUT /api/create-meta-recipe/` (already exists) |

Notes:
- `set_item_state` resolves the name via the existing alias-aware
  `helpers.find_ingredient`. If a name is ambiguous or unknown, the tool returns
  a clear error listing close matches so Claude can ask Tom.
- `get_recipes` is what makes Claude useful for substitutions: a protein slot
  already lists "pork mince OR chicken", so Claude can suggest swaps from real
  data before reaching for general world knowledge.
- Keep the tool set **small and well-described** — current Opus models reach for
  tools conservatively, so each tool's description states *when* to call it
  ("Call `set_item_state` when the user says they used up or ran low on
  something"), not just what it does.
- `create_meta_recipe` maps to the existing nested create/update endpoint — **no
  Django change needed**. Claude assembles the slots/options from the brainstorm;
  the endpoint auto-creates unknown ingredients. Passing an `id` updates an
  existing template (it rebuilds slots/bases). This + `log_cook` are the
  brainstorm→commit workflow Tom asked for.

## 6. Django API changes required (the gaps to close)

These are small, live on the Django side, and are the "make the API
MCP-ready" work. Each ships with a test.

1. **`log_cook` accepts `rating`, returns suggestions, mutates nothing.** Today
   the endpoint ignores `rating` though the model has the field (research.md §5).
   Add `rating`, and route creation through model validation so the "exactly one
   recipe link" rule is enforced (currently bypassed by `objects.create`).
   **Remove the old auto-deduct path** — instead return `used_ingredients` (base
   + slot choices) as a suggestion set. Pantry state is only ever changed by
   `set_item_state` after Tom confirms (presence-based pantry; never silently
   mutate from a cook log).
2. **New `POST /api/pantry/set-state/`** — `{ingredient, location?, state}`,
   resolves by name/alias, sets state, returns the item. Backs `set_item_state`.
   (Alternative: have the MCP `GET /api/pantry/` then `PATCH /api/pantry/<id>/`
   — but a by-name endpoint is cleaner and reusable.)
3. **Make the API matcher presence-based.** `what_can_i_cook` in `views.py`
   still compares quantities; the web matcher was already moved to presence
   (have-it beats have-enough). Apply the same change so the MCP and web agree.
4. **`bulk-pantry-add` restocks instead of duplicating.** It currently matches
   existing rows by `quantity__gt=0`, so adding an item that's marked Out
   creates a duplicate. Match by ingredient+location and set `state="in"`
   (mirror what the web `pantry_add` now does).
5. **Pantry serializer exposes `state`** — already true (`fields = "__all__"`),
   just confirm it in a test so it can't regress.

*Note:* `create_meta_recipe` needs **no** Django change — `POST/PUT
/api/create-meta-recipe/` already does nested create/update with ingredient
auto-creation. The brainstorm→commit path is otherwise pure MCP plumbing over
endpoints that exist; the only write-path gap is `log_cook`'s rating (item 1).

## 7. Project layout & dependencies

A small package in this repo, its own process — not bolted into Django:

```
mcp_server/
  __init__.py
  __main__.py        # FastMCP app; runs streamable-HTTP on 127.0.0.1:8765
  client.py          # thin httpx client around the Django API (caine token)
  tools.py           # the @mcp.tool definitions from §5
```

- Deps via a uv group so they only install where needed:
  `[dependency-groups] mcp = ["fastmcp", "httpx"]`. Deploy with
  `uv sync --group mcp` on the box that runs the service.
- The service holds no Django import — it's a pure HTTP client of `/api/`.
  Keeps the two deployables decoupled (Tom's "ai service" pattern).

## 8. Config (env, in `/var/lib/food/.env`)

| Var | Purpose |
|---|---|
| `FOOD_MCP_URL_SECRET` | the secret path segment nginx requires on `/mcp/<secret>/` (see §4) |
| `FOOD_API_BASE` | `http://127.0.0.1:8042/api` |
| `FOOD_API_TOKEN` | the `caine` DRF token |

All out of git; the systemd unit loads the same `.env` the Django service uses.

## 9. Deployment (sketch)

1. `uv sync --group mcp` on the box.
2. Add the three env vars to `/var/lib/food/.env`; generate the bearer token.
3. Install `deploy/food-mcp.service`, `daemon-reload`, start, enable.
4. Add the `location /mcp` block to the `food.jihakuz.xyz` nginx config
   (`proxy_buffering off`, long read timeout), `nginx -t`, reload.
5. In claude.ai, add a custom connector pointing at the **secret URL**
   `https://food.jihakuz.xyz/mcp/<secret>/` (authless connector — see §4).
6. Smoke test: in cooking mode, "what's in my pantry?" → Claude calls
   `get_pantry` and lists real items.

## 10. Conventions & error handling

- Tools return **structured, compact** results (names + states), not raw API
  JSON dumps — keep token cost down and make Claude's job easy.
- On a Django API error, the tool returns a short plain-language error
  (`is_error`) so Claude can relay or ask, never a stack trace.
- All writes are idempotent-ish: setting state to its current value is a no-op;
  adding an existing item restocks rather than duplicates.
- Read tools default to excluding `out` items unless asked — "what do I have"
  shouldn't list everything you're missing.

## 11. Testing

- **Django side:** unit tests for the new `set-state` endpoint, `log_cook`
  rating, presence-based API matcher, and bulk-add restock (extend
  `kitchen/tests.py`).
- **MCP side:** test `client.py` against a stub API; test each tool maps the
  right call and shapes results. The MCP server itself can be smoke-tested by
  pointing a local MCP client (or `curl` with the bearer) at it.

!! i should also be able to run the stack on this box and have you auth with it for testing

## 12. Open decisions to confirm before building

1. **claude.ai connector auth** — RESOLVED (§4): no static-bearer field exists,
   so use an **authless connector + secret in the URL path** (recommended), or
   OAuth/DCR if that feels too loose.
2. **Cook-log nudge — RESOLVED:** `log_cook` does **not** auto-change pantry
   state. It returns `used_ingredients` so Claude can *suggest* marking them
   Low/Out; Tom confirms, and the change goes through `set_item_state`. Never
   silently mutate the pantry from a cook log.
3. **Bearer in nginx vs app** — check the token in nginx, the FastMCP app, or
   both? Recommended: app (so it's in one place with the tools); nginx optional.

## Build order

1. Close the Django API gaps (§6) on a branch — small, test-covered, mergeable
   on their own.
2. Wire the URL-secret gate in nginx (§4) — `location /mcp/<secret>/` proxies,
   everything else 404s.
3. Build the FastMCP service (§5, §7) + systemd unit.
4. nginx `/mcp` + TLS, register the connector, smoke test.

## Definition of done

In claude.ai cooking mode, Tom can say "what can I make tonight?" and Claude
lists options grounded in the actual pantry; and "I used the last of the
noodles" updates the pantry — with no manual inventory typing, and the usual
cooking blocks intact.