docs(mcp): every create_* tool says what it is NOT for (#3123)

Scribe's record kinds get reached for interchangeably, and the moment of
choice is the only moment a correction is cheap. Rule 119 puts product
guidance in the instruction surfaces, so the docstring is where this
belongs — but a docstring that only documents parameters answers "how do I
call this" and leaves "should I be calling this at all" unasked.

The gap was lopsided. create_rule and start_planning already carried real
disambiguators; create_note — far and away the highest-volume surface —
carried none at all. The guidance sat in the rarest tool and was missing
from the most common one.

Each surface now opens with ONE deciding question in its own terms rather
than a pasted block:

  create_note     WHAT ELSE COULD HOLD THIS?      note is right when nothing
                                                  is owed and nothing enforces
  create_task     IS ANYTHING ACTUALLY OWED?      nothing owed -> note;
                                                  an arc -> start_planning
  create_snippet  SHAPE, OR ADVICE?               a snippet is code with a
                                                  LOCATION
  create_process  FOLLOWED, OR READ?              applies uninvoked -> rule

create_project_rule now points at the entity check too; it had only ever
covered rule-vs-rule scope.

The guard asserts STRUCTURE, never wording: each surface must name at least
two siblings. Pinning phrasing would make every improvement a test failure,
and a test that punishes editing is a test that gets deleted. Its second
half asserts the Args: block survives — the first check is satisfiable by
turning a docstring into an essay about the other tools, which would be a
worse contract than the one being fixed.

The guard caught two gaps on its first run, one of them its own: "design
system" is hard-wrapped across a line break in create_rule, so matching the
raw docstring reported it absent. _doc() now flattens whitespace. It also
caught start_planning naming only one alternative, which was true and is
now fixed.

Deliberately NOT built: an intent-router tool. It has a bootstrapping
problem — it is itself a tool that must be reached for — and MCP clients
already list every tool's description. Recorded in #3123; build it only if
wrong-surface reaches survive this.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/scribe/mcp/tools/tasks.py

@@ -135,6 +135,13 @@ async def create_task(
 ) -> dict:
     """Create a new task in Scribe.
 
+    IS ANYTHING ACTUALLY OWED? A task carries a status and someone is on the
+    hook to move it. If nothing is owed — you are recording what you learned,
+    decided or observed — that is a note (create_note), and filing it here
+    leaves a to-do nobody will ever close. If the work is an ARC of several
+    steps toward one goal, start_planning makes the milestone that holds
+    them; a task is one step, not the plan.
+
     Args:
         title: Task title (required).
         body: Markdown description / notes for the task.
@@ -323,7 +330,9 @@ async def start_planning(project_id: int, title: str) -> dict:
     Reach for this when the work has an ARC — several steps toward one goal,
     worth tracking as a unit. Work without one (a fix, a one-file change, a
     question answered) is a task, not a plan: create_task, drive its status, and
-    record progress with add_task_log. A milestone holding a single step is
+    record progress with add_task_log. A design or decision you are RECORDING
+    rather than executing is a note (create_note) — a plan nobody is going to
+    work through is a document filed in the place reserved for open work. A milestone holding a single step is
     ceremony, and it leaves the project with a plan that never meant anything.
 
     Creates a MILESTONE that IS the plan: its `body` is seeded with a design