Attester-Verify-Packages

# Verify packages before installing or importing

Use the attester.dev existence oracle before adding any third-party dependency or calling a library symbol you cannot confirm exists. The oracle answers from real published artifacts (PyPI wheels, npm tarballs), not from model memory.

This instruction exists because models invent plausible package names: a USENIX Security 2025 study measured 5.2% to 21.7% of suggested package names as nonexistent, depending on model and ecosystem.

When to check

- Before adding a package to a dependency file (`requirements.txt`, `pyproject.toml`, `package.json`) or running an install command for a package you did not choose yourself.

- Before writing an `import`, `require`, or `from ... import` for a third-party package.

- Before calling a function, class, or constant you cannot confirm exists in the target package.

- When a build fails on a missing package or symbol: check the name before changing anything else.

Skip the check for standard library modules, local project modules, and names already verified this session.

How to check

Free keyless endpoint, no account or API key. Quota: 25 calls per day per client IP, reset 00:00 UTC.

1. Package check: POST `https://attester.dev/demo/v1/package/exists` with body `{"ecosystem": "pypi" | "npm", "name": "<name>"}`. Proceed only when `exists` is `true`.

2. Symbol check: POST `https://attester.dev/demo/v1/symbol/exists` with body `{"ecosystem": "pypi" | "npm", "package": "<package>", "symbol": "<symbol>"}`. On a miss, prefer the `closest_match` suggestions over inventing variants.

On HTTP 429 (daily quota spent) or on network failure: state that the check was skipped and why, then continue with the most conservative option (prefer well-known packages and pinned versions).

What to do with answers

- `exists: true`: proceed. When pinning, prefer the version in `latest_version`.

- `exists: false`: do not install or import. Report the negative to the user together with the oracle's closest real names (`adjacent_to`, `closest_match`) and ask which one was meant.

- `typosquat_adjacent: true`: treat as a strong signal that the name is a typo or a hallucination. Never install the flagged name.

Higher volume

The free tier covers normal editing sessions. A paid route without the daily cap exists for high-volume use; see the service docs for details.