Portable Text Conversion

Organization

sanity-io

portable-text-conversion

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.

Overview

Publisher	sanity-io
Repository	`agent-toolkit`
Skill name	`portable-text-conversion`
Stars	184
Forks	28
Bundled files	3
License	MIT
Links	Skill source Repository Homepage

Markdown instructions
A SKILL.md file the model loads on demand, so it only costs tokens when a request actually matches.
Works with any LLM
AI skills are plain Markdown, not provider-specific code, so this works with GPT, Claude, Gemini, Grok, or a local model.
3 bundled files
Scripts, templates, and references the model can read while it works. Files are read-only and never executed.
Open source
Published by sanity-io on GitHub. Read the source before you install it.

Installation

Install the Portable Text Conversion AI skill in TypingMind to use it with any LLM, or drop it into another agent that reads SKILL.md.

Install in TypingMind

TypingMind installs a skill straight from its GitHub folder — it reads SKILL.md, bundles the resource files, and stores the result locally.

Open the app and go to Plugins → Skills.
Choose "Install from GitHub".
Paste the skill folder URL below and confirm.
Enable the skill in any chat where you want it available.

Plugins → Skills → Add skill → From GitHub URL, then paste the folder URL and press Continue.

Install in another agent

Any agent that reads the Agent Skills format can use this skill — copy the folder into that agent's skills directory.

Claude Code — .claude/skills

git clone --depth 1 https://github.com/sanity-io/agent-toolkit.git /tmp/agent-toolkit
mkdir -p .claude/skills
cp -r /tmp/agent-toolkit/skills/portable-text-conversion .claude/skills/portable-text-conversion

Restart Claude Code after copying so it picks up the new skill.

Use it in TypingMind

Enable Portable Text Conversion in any TypingMind chat and the model takes it from there. Its name and description sit in the system prompt, and the moment a request matches, the model loads the full instructions itself — you never invoke it by hand, and it costs no tokens until it is actually used.

The model loads Portable Text Conversion on its own as soon as a request matches it.

Works with any AI model

AI skills are plain Markdown instructions rather than provider-specific code, so Portable Text Conversion is not tied to the model it was written for. Install it once in TypingMind and use it with GPT-5, Claude, Gemini, Grok, DeepSeek, Mistral, Llama, or a local model you run yourself — all on your own API keys.

Loaded only when it is needed
The system prompt carries just the name and description. The instructions are fetched on the first matching request, so an idle skill costs nothing.
Switch models mid-chat
Because the skill is instructions rather than code, changing model does not break it — the next model reads the same SKILL.md.

Skill instructions

This is the SKILL.md content the model loads. Read it before installing — a skill is instructions your model will follow.

Portable Text Conversion

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

markdownToPortableText — Convert Markdown directly using @portabletext/markdown (recommended for Markdown)
htmlToBlocks — Parse HTML into PT blocks using @portabletext/block-tools (for HTML migration)
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

Note: @sanity/block-tools is the legacy package name. Always use @portabletext/block-tools for new projects. The API is the same.

Bundled files

The model reads these on demand while the skill is loaded. They are exposed as readable files and are never executed.

Frequently asked questions

What does the Portable Text Conversion AI skill do?

Why use Portable Text Conversion on TypingMind?

Because you install it once and use it with any model. Portable Text Conversion is plain Markdown rather than provider-specific code, so the same skill runs on GPT-5, Claude, Gemini, Grok, or a local model — and you can switch model mid-chat without it breaking. TypingMind runs on your own API keys, so you pay providers directly instead of a per-seat subscription, and your skills and chats stay in your own storage.

How do I install Portable Text Conversion in TypingMind?

Open Plugins → Skills → Install from GitHub in TypingMind and paste https://github.com/sanity-io/agent-toolkit/tree/main/skills/portable-text-conversion. TypingMind reads its SKILL.md and bundles its files and installs it as a skill you can enable per chat.

Which AI models can use Portable Text Conversion?

Any model you connect in TypingMind. AI skills are plain Markdown instructions rather than provider-specific code, so GPT, Claude, Gemini, Grok, and local models can all load this skill when a request matches it.

How many AI models can I use with Portable Text Conversion?

As many as you like. As long as a model supports skills, you can use Portable Text Conversion with it — GPT, Claude, Gemini, Grok, DeepSeek, Mistral, Llama and more — all on TypingMind with your own API keys.

Is the Portable Text Conversion AI skill free?

Yes. It is published on GitHub by sanity-io under the MIT license. You only pay your own AI provider for the tokens you use.

What are AI skills?

An AI skill is a reusable instruction bundle that teaches an AI model how to do one specific task. It follows the open Agent Skills format: a SKILL.md file with a name and description, plus any scripts, templates or reference files the model may need. The model reads the instructions only when your request matches the skill, so an installed skill costs nothing until it is used.

How are AI skills different from plugins or MCP servers?

A plugin or MCP server gives a model new tools to call — code that runs somewhere and returns a result. An AI skill gives the model knowledge and process instead: how to approach a task, which steps to follow, what good output looks like. Skills are plain Markdown, so they need no server, no API key and no runtime, and they work with any model.

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Overview

Installation

Install in TypingMind

Install in another agent

Use it in TypingMind

Works with any AI model

Skill instructions

Portable Text Conversion

Portable Text Specification

Conversion Rules

Bundled files

Frequently asked questions

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