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add-license

Add a LICENSE file to a repository by fetching the official license text from SPDX.

Dual-purpose Tutorials
This how-to was written to be readable by both humans and machines. This box marks the spot where user-provided context would normally be inserted for the machine.

Process​

Step 0: Gather license requirements​

Determine the following from context or by asking:

  • License type: The SPDX identifier (e.g., MIT, Apache-2.0, GPL-3.0-only)
  • Copyright holder: Name of the person or organization (infer from package config like pyproject.toml author, package.json author, or Cargo.toml authors)
  • Copyright year: Default to the current year unless specified otherwise

Common SPDX license identifiers (non-exhaustive):

  • MIT — MIT License
  • Apache-2.0 — Apache License 2.0
  • GPL-3.0-only — GNU General Public License v3.0
  • LGPL-3.0-only — GNU Lesser General Public License v3.0
  • MPL-2.0 — Mozilla Public License 2.0
  • BSL-1.0 — Boost Software License 1.0
  • Unlicense — The Unlicense
  • AGPL-3.0-only — GNU Affero General Public License v3.0
  • BSD-3-Clause — BSD 3-Clause License
  • BSD-2-Clause — BSD 2-Clause License

Step 1: Check current license state​

Check if a LICENSE file already exists:

ls LICENSE* 2>/dev/null || echo "No LICENSE file found"

If a LICENSE file already exists, ask the user if they want to replace it.

Step 2: Fetch official license text​

Fetch the canonical license text directly from SPDX's GitHub repository using curl:

curl -s "https://raw.githubusercontent.com/spdx/license-list-data/main/text/<SPDX-ID>.txt"

This fetches the authoritative plain text with zero LLM involvement—no hallucination risk.

Step 3: Create the LICENSE file​

Replace placeholders in the fetched text and write to LICENSE:

  • <year> → copyright year
  • <copyright holders> → copyright holder name

Use sed to replace placeholders and write the file:

curl -s "https://raw.githubusercontent.com/spdx/license-list-data/main/text/<SPDX-ID>.txt" \
  | sed "s/<year>/<YEAR>/g; s/<copyright holders>/<COPYRIGHT_HOLDER>/g" \
  > LICENSE

Step 4: Verify​

Verify the LICENSE file was created and contains the complete license text:

head -20 LICENSE

Step 5: Commit​

Ask the user if they want to commit, then use the committer agent.

Key Principles​

  • Always fetch license text from SPDX using curl—no LLM token waste or hallucination risk.
  • Infer copyright holder from existing package config when possible.
  • Use LICENSE (no extension) as the standard filename.