# portable-text-conversion

Turns HTML and Markdown into Portable Text blocks for Sanity. Useful when migrating content off a legacy CMS or building an import pipeline.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 2700 installs · ★ 194
- Author: sanity
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/sanity-io/agent-toolkit/tree/HEAD/skills/portable-text-conversion/SKILL.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/skills/portable-text-conversion

## What it does

The skill lays out three conversion routes. Markdown goes through `markdownToPortableText` from `@portabletext/markdown`, which the author recommends as the default choice. HTML goes through `htmlToBlocks` from `@portabletext/block-tools`. The third route is manual: build blocks yourself when the source is an API or a database rather than markup.

It also documents the Portable Text spec — an array of blocks, each with `_type`, `_key`, `children` holding spans, and `markDefs` for annotations. Lists live on regular blocks via `listItem` and `level`. The rules sit in separate files: `rules/markdown-to-pt.md`, `rules/html-to-pt.md`, `rules/manual-construction.md`. The agent reads whichever matches your source format.

Watch the package names. `@sanity/block-tools` is the legacy one; new projects should pull `@portabletext/block-tools`, and the API is identical. If your repo still carries the old package, check whether it comes in through another dependency.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add sanity-io/agent-toolkit --skill portable-text-conversion -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/portable-text-conversion/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/portable-text-conversion/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add sanity-io/agent-toolkit --skill portable-text-conversion -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/portable-text-conversion/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add sanity-io/agent-toolkit --skill portable-text-conversion -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/portable-text-conversion/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install sanity-io/agent-toolkit portable-text-conversion
```

2. **Manually: put the files in place**
- File: `.github/skills/portable-text-conversion/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add sanity-io/agent-toolkit --skill portable-text-conversion -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/sanity-io/agent-toolkit --path skills/portable-text-conversion
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/portable-text-conversion/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add sanity-io/agent-toolkit --skill portable-text-conversion -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/sanity-io/agent-toolkit/tree/HEAD/skills/portable-text-conversion/SKILL.md

## When to use it
- migrate articles from a legacy CMS into Sanity
- import Markdown files as Portable Text documents
- build a pipeline that ingests HTML from an external source
- construct blocks by hand from API or database rows
- figure out how `_key`, `markDefs` and lists work in Portable Text

## Example prompts
- Convert this Markdown into Portable Text blocks with `markdownToPortableText`
- Parse this HTML page into PT blocks using `htmlToBlocks` and show the output
- Build a Portable Text block array by hand from this data

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 655139be949ed9da.

BEGIN THIRD-PARTY FILE 655139be949ed9da
````text
---
name: portable-text-conversion
description: Convert HTML and Markdown content into Portable Text blocks for Sanity. Use when migrating content from legacy CMSs, importing HTML or Markdown into Sanity, building content pipelines that ingest external content, converting rich text between formats, or programmatically creating Portable Text documents. Covers @portabletext/markdown (markdownToPortableText), @portabletext/block-tools (htmlToBlocks), custom deserializers, and the Portable Text specification for manual block construction.
license: MIT
metadata:
  author: sanity
  version: "1.0.0"
---

# Portable Text Conversion

Convert external content (HTML, Markdown) into Portable Text for Sanity. Three main approaches:

1. **`markdownToPortableText`** — Convert Markdown directly using `@portabletext/markdown` (recommended for Markdown)
2. **`htmlToBlocks`** — Parse HTML into PT blocks using `@portabletext/block-tools` (for HTML migration)
3. **Manual construction** — Build PT blocks directly from any source (APIs, databases, etc.)

## Portable Text Specification

Understand the target format before converting. PT is an array of blocks:

```json
[
  {
    "_type": "block",
    "_key": "abc123",
    "style": "normal",
    "children": [
      {"_type": "span", "_key": "def456", "text": "Hello ", "marks": []},
      {"_type": "span", "_key": "ghi789", "text": "world", "marks": ["strong"]}
    ],
    "markDefs": []
  },
  {
    "_type": "block",
    "_key": "jkl012",
    "style": "h2",
    "children": [
      {"_type": "span", "_key": "mno345", "text": "A heading", "marks": []}
    ],
    "markDefs": []
  },
  {
    "_type": "image",
    "_key": "pqr678",
    "asset": {"_type": "reference", "_ref": "image-abc-200x200-png"}
  }
]
```

**Key rules:**
- Every block and span needs `_key` (unique within the array)
- `_type: "block"` is for text blocks; custom types use their own `_type`
- `markDefs` holds annotation data; `marks` on spans reference `markDefs[*]._key` or are decorator strings
- Lists use `listItem` ("bullet" | "number") and `level` (1, 2, 3...) on regular blocks

## Conversion Rules

Read the rule file matching your source format:

- **Markdown → Portable Text**: `rules/markdown-to-pt.md` — `@portabletext/markdown` with `markdownToPortableText` (recommended)
- **HTML → Portable Text**: `rules/html-to-pt.md` — `@portabletext/block-tools` with `htmlToBlocks`
- **Manual PT Construction**: `rules/manual-construction.md` — build blocks programmatically from any source
````
END THIRD-PARTY FILE 655139be949ed9da

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