ToneCraft is a Thunderbird extension that detects (and blocks) unprofessional language in outgoing emails and suggests polite alternatives. It helps you maintain a courteous tone and avoid accidental rudeness.

PS: Extension tested (also manually) but it was written by: qwen3-coder-next, qwen3.5-122 and GLM-4.7 on OpenCode.

Download: https://addons.thunderbird.net/thunderbird/addon/tonecraft/

• Detect unprofessional tone in outgoing emails
• Provide suggested rewrites that are more polite
• "Ignore and Send Anyway" button to bypass the suggestion

git clone <repo-url>
cd ToneCraft
npm install
web-ext run

1. Open Thunderbird → Add‑ons → Extensions → Install Add‑on From File.
2. Select the folder dist generated after npm run build or the XPI file.

1. Download tonecraft.xpi from the releases page.
2. In Thunderbird, go to Add‑ons → Extensions → Install Add‑on From File and choose the XPI.

Open the extension settings page via the gear icon in the Thunderbird toolbar.

Provide one of the following examples:

• OpenAI: https://api.openai.com/v1/chat/completions
• Ollama: http://localhost:11434/api/chat

Paste your API key in the "API Key" field. The key is stored only in your local browser profile.

Select a model (e.g., gpt-4o, claude-3-sonnet, llama3) and optionally edit the prompt that guides the tone suggestions.

When you compose a new email and click Send, the extension analyses the text.

• If the tone is unprofessional, a warning appears with a suggested rewrite.
• You can click Ignore and Send Anyway to bypass the suggestion.

• Invalid API key – Double‑check the key and the endpoint URL.
• Timeout – Ensure your network allows outgoing requests to the AI service.
• No response – Verify the model name is correct and the service is reachable.

Your API key never leaves your computer. It is stored locally in the extension storage and is not sent to any third‑party server.