Player.json and client.player.json Usage in marketplace addons

For Marketplace-bound, cooperative, additive-only Bedrock add-ons, the relevant guidance is about not modifying vanilla gameplay files or shared/global elements. While the context does not name player.json or client.player.json explicitly, it does define the general rule that applies to them:

1. Do not change or remove vanilla behavior

• Cooperative add-ons “should not change or remove vanilla behavior; only add new things to the game.”
• It is explicitly stated that creators “should not change any of the vanilla gameplay files or use scripting to disable vanilla gameplay elements.”
• The reason is to ensure that multiple add-ons can work together and that future vanilla updates are not broken by overrides.
• player.json and client.player.json are core vanilla definitions for the player, so editing or overriding them would fall under “changing vanilla gameplay files,” which is discouraged for cooperative/Marketplace scenarios.

2. Only add new content instead of overriding shared definitions

• The guidelines emphasize: “In addition to vanilla gameplay, you should not change or update vanilla elements… To prevent Add-Ons from unintentionally disabling another Add-On, we only allow new things to be created.”
• Overriding player.json or client.player.json is a direct update to a vanilla element that every world and every other add-on depends on, which risks conflicts and is therefore against these cooperative guidelines.

3. Use unique namespaces and new identifiers instead

• The recommended pattern is to create new entities, items, etc., with unique namespaces rather than altering existing ones.
• Namespacing guidance is given specifically to avoid collisions and ensure compatibility with other add-ons.
• For player-related features, the compliant approach is to:
  • Add new entities, items, or mechanics with unique identifiers and namespaces.
  • Avoid directly editing the player’s core JSON definitions.

4. Marketplace/cooperative implication

• Marketplace add-ons are expected to follow these cooperative, additive-only rules so they can coexist with other Marketplace content.
• Because of that, using player.json and client.player.json to override or modify the vanilla player is not aligned with the documented guidelines for cooperative add-ons.

In practice, for a Marketplace add-on, the safe and guideline-compliant approach is:

• Do not ship overrides of player.json or client.player.json.
• Implement player-facing features via new entities, items, mechanics, and UI that use unique namespaces and do not modify vanilla player definitions.

References:

• Guidelines for Building Cooperative Add-Ons
• Namespacing and Identifiers
• Comprehensive List of Add-On Pack Contents
• Client Entity JSON and Introduction