nuget-fetcher

name	nuget-fetcher
description	Fetch NuGet package metadata, versions, vulnerabilities, compat matrix, and deprecation status. Supports dotnet list package and NuGet.org v3 API.
argument-hint	<package name> [--version <v>]
effort	low

nuget-fetcher

Retrieve concrete NuGet package facts — no hallucinated versions or APIs.

Primary Commands

# In a project directory
dotnet list package                              # installed
dotnet list package --outdated                   # available upgrades
dotnet list package --vulnerable --include-transitive
dotnet list package --deprecated

# Global / without project
# v3 Registration index
curl -s "https://api.nuget.org/v3/registration5-semver1/<id>/index.json"
# Service discovery
curl -s "https://api.nuget.org/v3/index.json"
# Catalog (historical releases)
curl -s "https://api.nuget.org/v3/catalog0/index.json"

What to Retrieve

Per package:

• Latest stable version + pre-release if diverged
• Publish date of latest version
• Supported target frameworks (from .nuspec)
• Dependencies (direct only — deep trees are noise)
• License + license expression
• Repository URL + last-commit signal
• Known CVEs (via --vulnerable or GitHub Advisory)
• Deprecation status

Flow

1. Normalize package id (case-insensitive on NuGet.org)
2. Query NuGet.org registration endpoint OR use dotnet list package inside the project
3. Extract version, frameworks, deps, license
4. Cross-check CVE via dotnet list package --vulnerable
5. Output compact summary — not raw JSON

Iron Laws

• Never fabricate a version number
• Verify the package id exactly (typosquatting risk)
• Flag --vulnerable matches as security-critical
• Prefer official MS-owned packages when equivalent community package is unmaintained

Output Template

# Polly — NuGet metadata

| Field | Value |
|-------|-------|
| Latest | 8.4.0 (stable) |
| Published | 2026-03-20 |
| Target frameworks | net6.0, net8.0, net9.0 |
| License | BSD-3-Clause |
| Repository | github.com/App-vNext/Polly |
| Vulnerabilities | none |
| Deprecated | no |

## Direct deps (latest)
- Microsoft.Bcl.AsyncInterfaces ≥ 6.0.0

## Notable
- v8 is a major rewrite with breaking API changes from v7
- `Microsoft.Extensions.Http.Resilience` wraps Polly for HttpClient

Integration

Used by:

• nuget-researcher agent (library evaluation)
• /dotnet:research --library skill
• /dotnet:plan when evaluating deps
• audit / techdebt skills

References

• ${CLAUDE_SKILL_DIR}/references/nuget-api.md — v3 endpoints, registration, flat container, search
• ${CLAUDE_SKILL_DIR}/references/vuln-sources.md — GHSA, NuGet advisories, --vulnerable limits
• ${CLAUDE_SKILL_DIR}/references/framework-monikers.md — TFM compatibility reference

Anti-patterns

• Returning raw JSON — users want the summary
• Ignoring --vulnerable results
• Not distinguishing stable from pre-release when user asked for stable
• Recommending a package without verifying its id exactly