uv-metadata

Inspect any Python package metadata from any source without installing.

$ uvx uv-metadata requests -kversion
2.32.4

$ uvx uv-metadata requests -krequires_python
>=3.10

$ uvx uv-metadata 'pip<23' -kversion
22.3.1

Works with published packages, local wheels/sdists, project folders, and git repos. For published packages, metadata is streamed directly from the remote wheel via HTTP range requests — typically a few KB, no full download needed.

Why this is useful

Getting package metadata as JSON from a simple CLI opens up a lot of possibilities:

• Scripting: what's the latest version of a package? What about the last 2.x release? What's the latest version that still supports Python 3.7? (uvx uv-metadata -p3.7 setuptools -kversion)
• Validation: CI checks that verify your package metadata is complete before publishing — are author, URL, license, classifiers all present?
• Verifying your own project: after setting up dynamic versioning (e.g. setuptools-scm), just run uvx uv-metadata . to confirm your metadata looks right — no need to build or install
• Dependency auditing: quickly check what a package requires, what Python versions it supports, or what entry points it exposes — all without installing anything

This project also serves as a reference implementation for a proposed native uv metadata subcommand (see astral-sh/uv#6037 and the spec).

Requires uv on PATH.

Installation

# Run directly (no install needed)
uvx uv-metadata requests

# Or install permanently
uv tool install uv-metadata

Quick examples

# Full metadata as JSON
uvx uv-metadata flask

# Single key
uvx uv-metadata flask -kversion

# Version constraint
uvx uv-metadata 'flask<3' -kversion

# Local project
uvx uv-metadata .

# Local wheel or sdist
uvx uv-metadata ./dist/mypackage-1.0.0-py3-none-any.whl

# Git repo
uvx uv-metadata git+https://github.com/psf/requests@main

# Target a specific Python version
uvx uv-metadata numpy -p3.9 -kversion

Input routing

Output format

JSON with sorted keys. The description (long description) field is omitted by default as it is typically very large; use --full to include it.

$ uvx uv-metadata pip
{
    "author_email": "The pip developers <distutils-sig@python.org>",
    "classifiers": [
        "Development Status :: 5 - Production/Stable",
        ...
    ],
    "description_content_type": "text/x-rst",
    "entry_points": {
        "console_scripts": {
            "pip": "pip._internal.cli.main:main",
            "pip3": "pip._internal.cli.main:main"
        }
    },
    "license_expression": "MIT",
    "metadata_version": "2.4",
    "name": "pip",
    "project_url": [
        "Documentation, https://pip.pypa.io",
        "Source, https://github.com/pypa/pip"
    ],
    "requires_python": ">=3.9",
    "summary": "The PyPA recommended tool for installing Python packages.",
    "version": "26.0.1"
}

Structural rules:

• Keys are lower_snake_case
• Single-occurrence fields: plain string
• Multi-occurrence fields: list of strings
• entry_points: {"group": {"name": "module:attr"}}
• top_level: list of top-level importable names
• UNKNOWN values are omitted

CLI reference

usage: uv-metadata [-h] [-p PYTHON] [-k KEY] [--full] [package]

Output the metadata of a package, in machine-readable format

positional arguments:
  package              Package to inspect (default: current folder)

options:
  -h, --help           show this help message and exit
  -p, --python PYTHON  Python version to target (e.g. 3.11)
  -k, --key KEY        Show only this key from the metadata
  --full               Include full description in output

How it works

Fast path for published packages

1. uv pip compile --format pylock.toml resolves to a concrete wheel URL without downloading
2. SeekableHttpFile + ZipFile streams only the dist-info files via HTTP range requests
3. Falls back to downloading the sdist when no wheel is available

Unified metadata reading

All extraction strategies produce a dist-info folder which is read by importlib.metadata.PathDistribution. Both METADATA (wheels) and PKG-INFO (sdists) are handled transparently.

Archive extraction

A MetadataReader base class with ZipReader and TarReader implementations provides uniform member discovery and extraction across archive formats.

Dependencies

Relevant PEPs

• PEP 241 – Metadata for Python Software Packages 1.0
• PEP 314 – Metadata for Python Software Packages 1.1
• PEP 345 – Metadata for Python Software Packages 1.2
• PEP 566 – Metadata for Python Software Packages 2.1
• PEP 508 – Dependency specification for Python Software Packages
• PEP 517 – A build-system independent format for source trees
• PEP 643 – Metadata for Package Source Distributions
• PEP 658 – Serve Distribution Metadata in the Simple Repository API
• PEP 639 – Improving License Clarity with Better Package Metadata