Jspecify Nullness

Community

alexandru

jspecify-nullness

JSpecify nullness annotations for Java APIs and tooling. Use when adopting or migrating JSpecify annotations, designing null-safe Java signatures, fixing generic bounds and type-use placement, or interpreting Kotlin interop, annotation-processor, and tool-conformance behavior.

Overview

Publisher	alexandru
Repository	`skills`
Skill name	`jspecify-nullness`
Stars	51
Forks	3
Bundled files	2
Links	Skill source Repository

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.
2 bundled files
Scripts, templates, and references the model can read while it works. Files are read-only and never executed.
Open source
Published by alexandru on GitHub. Read the source before you install it.

Installation

Install the Jspecify Nullness 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.
https://github.com/alexandru/skills/tree/main/skills/coding/jspecify-nullness
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/alexandru/skills.git /tmp/skills
mkdir -p .claude/skills
cp -r /tmp/skills/skills/coding/jspecify-nullness .claude/skills/jspecify-nullness

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

Use it in TypingMind

Enable Jspecify Nullness 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 Jspecify Nullness 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 Jspecify Nullness 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.

JSpecify Nullness (Java)

Quick start

Add org.jspecify:jspecify:1.0.0 as a visible API dependency for Java libraries.
Prefer @NullMarked at package or class scope; add @Nullable only where null is allowed.
Treat unannotated types outside @NullMarked as unspecified nullness, not non-null.
Decide generic bounds deliberately: <T extends @Nullable Object> accepts nullable type arguments; <T> does not in a null-marked scope.
Keep @Nullable/@NonNull in JSpecify-recognized type-use locations, especially for arrays, nested types, type arguments, and bounds.
Read references/jspecify-nullness.md before substantial annotation, migration, or tooling advice.

Workflow

Confirm consumer constraints: nullness checker, Kotlin compiler behavior, and annotation processors.
Add the JSpecify dependency without hiding it from downstream users.
Annotate nullable types first, then add @NullMarked at class or package scope.
Fix generics: choose nullable/non-null bounds and annotate type-variable uses only when the use differs from the type argument.
Compile examples for syntax, then run a JSpecify-aware nullness analyzer and fix findings before expanding scope.

Rules of thumb

Do not annotate local-variable root types or casts; annotate only nested type arguments/components there.
For fields, parameters, and returns, @Nullable String[] means nullable elements; String @Nullable [] means the array reference is nullable.
For nested types, annotate the nested type as Map.@Nullable Entry, not the outer type.
Use @NonNull T only to force a type-variable use non-null when the type argument may be nullable.
Use @NullUnmarked only as an incremental escape hatch inside a null-marked scope.

Output expectations

Provide annotated signatures and call-site implications.
Explain generic bound choices and type-use placement.
Call out tool-conformance limits instead of promising specific diagnostics.
For skill edits, run jbang skills/coding/jspecify-nullness/scripts/verify-examples.java.

References

Load references/jspecify-nullness.md for source-backed guidance, examples, and representative prompts.

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 Jspecify Nullness AI skill do?

Why use Jspecify Nullness on TypingMind?

Because you install it once and use it with any model. Jspecify Nullness 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 Jspecify Nullness in TypingMind?

Open Plugins → Skills → Install from GitHub in TypingMind and paste https://github.com/alexandru/skills/tree/main/skills/coding/jspecify-nullness. 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 Jspecify Nullness?

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 Jspecify Nullness?

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

Is the Jspecify Nullness AI skill free?

It is published on GitHub by alexandru. Check the repository for licensing terms. 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

JSpecify Nullness (Java)

Quick start

Workflow

Rules of thumb

Output expectations

References

Bundled files

Frequently asked questions

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