---
title: "Start Writing"
method: POST
path: "/api/mcp/start_writing"
tags: ["mcp"]
---

# Start Writing

`POST /api/mcp/start_writing`

## Request

- Base URL: `https://writer.swapp1990.org` (the document declares no server; this is the origin it was published from)
- URL: `https://writer.swapp1990.org/api/mcp/start_writing`
- Auth: none declared

Commit the current outline + cast and kick off chapter writing.

The single action that advances a story from 'reviewing' into
writing. Replaces the old two-step Apply-outline → Apply-cast
flow: the review screen edits both together, and this endpoint
starts the writer regardless of which tab the user was on.

## Request body

- ApplyCharactersInput
  - `job_id` string, required: The story job ID.
  - `model` string, nullable: Model override for chapter generation.
  - `target_words_per_chapter` integer, nullable: Per-chapter word target override applied to the writer.

## Response `200`

Successful Response

- StoryMutationResponse
  - `job_id` string, nullable
  - `status` string, nullable
  - `story_url` string, nullable
  - `chapter` integer, nullable
  - `kind` string, nullable

## Other responses

- `422`: Validation Error

---

[API](https://skmtc.dev/swapp1990/apis/writeforyou-mcp-api.md) · [All operations](https://skmtc.dev/swapp1990/apis/writeforyou-mcp-api/llms.txt) · [OpenAPI document](https://skmtc.dev/swapp1990/apis/writeforyou-mcp-api/revisions/ce5e2a89ab4d?raw)