JavaScript / CLI / Action / MCP
dev-error-explainers.
Explain a developer error without an LLM.
Seven deterministic JavaScript explainers, shared with six iloveblogs browser tools. Use the library offline, in a terminal, in CI or through an MCP client.
Start with the exact error
The library matches known error signatures and returns a structured explanation: the rule, the severity, the cause and the suggested fixes. Its modules cover CORS, ESM/CommonJS, npm dependency conflicts, stale chunks, database URLs, database connections and Next.js builds. An unrecognised input is reported as unrecognised. It does not ask a language model to fill in a diagnosis.
The same logic in several places
The public package exposes the pure JavaScript functions, a command-line interface, a GitHub Action and a stdio MCP server with an explain_error tool. Six modules also power the browser tools on iloveblogs. That gives readers a path from an interactive explanation to the exact source file. The seventh module, for database connection errors, currently belongs to the library only.
A contract readers can check
The repository includes a documented output contract and a fixture corpus. The tests run each fixture through diagnose() and check the stable expected result. CLI, Action and MCP inputs are masked for recognisable secret patterns before analysis, with the limits documented in the contract. The database URL doctor has a separate handling path. Read those limits before choosing what to paste into an integration.
Try a documented example
window is not defined
From a checkout of the repository, use the public fixture. Its expected result identifies the rule below.
npx dev-error-explainers --json < fixtures/next-build/window-undefined/input.txtrule: next-build.window-undefined