VSIX package json errors — check extension package blockers before

Lints a VS Code extension package.json for the manifest mistakes that make vsce package/publish fail or ship a broken listing. 14 rules, offline. Runs entirely in your browser — nothing is uploaded.

as of

Free here: Lints the extension manifest you have open and names every publish blocker with the exact field to change. In the editor: Lints every extension manifest in the workspace in one pass and writes the result out as a JSON/SARIF file you own for CI — that part asks for a licence key.

Same engine as the VS Code extension, byte for byte.