firebase-basics — Claude Code skill: install and use

---
name: firebase-basics
metadata:
  category: Serverless
description: >-
  Provides foundational Firebase CLI setup, CLI installation, version checks (`firebase-tools@latest --version`), CLI login (including --no-localhost), project creation, project selection (`firebase use`), and app config file downloads (`google-services.json`, `GoogleService-Info.plist`). Use ONLY for CLI login, project creation/switching, or downloading app config files. Don't use for Firebase Hosting deploy, Firestore, Auth, App Hosting, Data Connect, Crashlytics, or Remote Config.
---

# Firebase Basics

## Prerequisites

Complete these setup steps before proceeding:

1.  **Local Environment Setup:** Verify the environment is properly set up so we
    can use Firebase tools:

    -   Run `npx -y firebase-tools@latest --version` to check if the Firebase
        CLI is installed.
    -   Verify if the Firebase MCP server is installed using your existing
        tools.
    -   **CRITICAL**: Before configuring any extensions or agent environments
        below, you MUST read
        [references/local-env-setup.md](references/local-env-setup.md).
    -   **DO NOT SKIP** this step: if 'firebase-basics' is the only Firebase
        skill available to you, you must follow the reference for your agent
        environment to set up the full suite of Firebase skills:
        -   **Gemini CLI**: Review
            [references/setup/gemini_cli.md](references/setup/gemini_cli.md)
        -   **Antigravity**: Review
            [references/setup/antigravity.md](references/setup/antigravity.md)
        -   **Android Studio**: Review
            [references/setup/android_studio.md](references/setup/android_studio.md)
        -   **Claude Code**: Review
            [references/setup/claude_code.md](references/setup/claude_code.md)
        -   **Cursor**: Review
            [references/setup/cursor.md](references/setup/cursor.md)
        -   **GitHub Copilot**: Review
            [references/setup/github_copilot.md](references/setup/github_copilot.md)
        -   **Other Agents**: Review
            [references/setup/other_agents.md](references/setup/other_agents.md)

1.  **Authentication:** Ensure you are logged in to Firebase so that commands
    have the correct permissions. Run `npx -y firebase-tools@latest login`. For
    environments without a browser (e.g., remote shells), use `npx -y
    firebase-tools@latest login --no-localhost`.

    -   The command should output the current user.
    -   If you are not logged in, follow the interactive instructions from this
        command to authenticate.

1.  **Active Project:** Most Firebase tasks require an active project context.

    > [!IMPORTANT] **For Agents:** Before proceeding with project configuration,
    > you MUST pause and ask the developer if they prefer to:
    >
    > 1.  **Provide an existing Firebase Project ID**, or
    > 1.  **Create a new Firebase project**.

    -   **If using an existing Project ID:**

        1.  Check the current project by running `npx -y firebase-tools@latest
            use`.
        1.  If the command outputs `Active Project: <project-id>`, confirm with
            the user if this is the intended project.
        1.  If not, or if no project is active, set the project provided by the
            user:

        ```bash
        npx -y firebase-tools@latest use <PROJECT_ID>
        ```

    -   **If creating a new project:** Run the following command to create it:

        ```bash
        npx -y firebase-tools@latest projects:create <project-id> --display-name "<display-name>"
        ```

        *Note: The `<project-id>` must be 6-30 characters, lowercase, and can
        contain digits and hyphens. It must be globally unique.*

## Firebase Usage Principles

Adhere to these principles:

1.  **Use npx for CLI commands:** To ensure you always use the latest version of
    the Firebase CLI, always prepend commands with `npx -y
    firebase-tools@latest` instead of just `firebase`. For example, use `npx -y
    firebase-tools@latest --version`. NEVER suggest the naked `firebase` command
    as an alternative.
1.  **Prioritize official knowledge:** For any Firebase-related knowledge,
    consult the `developerknowledge_search_documents` MCP tool before falling
    back to Google Search or your internal knowledge base. Including "Firebase"
    in your search query significantly improves relevance.
1.  **Follow Agent Skills for implementation guidance:** Skills provide
    opinionated workflows (CUJs), security rules, and best practices. Always
    consult them to understand *how* to implement Firebase features correctly
    instead of relying on general knowledge.
1.  **Use Firebase MCP Server tools instead of direct API calls:** Whenever you
    need to interact with remote Firebase APIs (such as fetching Crashlytics
    logs or executing Data Connect queries), use the tools provided by the
    Firebase MCP Server instead of attempting manual API calls.
1.  **Keep Plugin / Agent Skills updated:** Since Firebase best practices evolve
    quickly, regularly check for and install updates to their Firebase plugin or
    Agent Skills. Similarly, if you encounter issues with outdated tools or
    commands, follow the steps below based on your agent environment:
    -   **Antigravity**: Follow
        [references/refresh/antigravity.md](references/refresh/antigravity.md)
    -   **Gemini CLI**: Follow
        [references/refresh/gemini-cli.md](references/refresh/gemini-cli.md)
    -   **Claude Code**: Follow
        [references/refresh/claude.md](references/refresh/claude.md)
    -   **Cursor**: Follow
        [references/refresh/other-agents.md](references/refresh/other-agents.md)
    -   **Android Studio**: Follow
        [references/refresh/android_studio.md](references/refresh/android_studio.md)
    -   **Others**: Follow
        [references/refresh/other-agents.md](references/refresh/other-agents.md)
1.  **Automate Config File Retrieval:** When setting up iOS or Android apps, do
    NOT direct users to the Firebase Console to download `google-services.json`
    or `GoogleService-Info.plist`. Instead, use the Firebase CLI to fetch the
    config programmatically:
    -   For Android: `npx -y firebase-tools@latest apps:sdkconfig ANDROID
        <APP_ID> --project <PROJECT_ID>`
    -   For iOS: `npx -y firebase-tools@latest apps:sdkconfig IOS <APP_ID>
        --project <PROJECT_ID>` Save the output to the appropriate location
        (e.g., `app/google-services.json` for Android, or a path to be linked by
        `xcode-project-setup` for iOS).

## References

-   **Initialize Firebase:** See
    [references/firebase-service-init.md](references/firebase-service-init.md)
    when you need to initialize new Firebase services using the CLI.
-   **Exploring Commands:** See
    [references/firebase-cli-guide.md](references/firebase-cli-guide.md) to
    discover and understand CLI functionality.
-   **SDK Setup:** For detailed guides on adding Firebase to your app:
    -   **Web**: See [references/web_setup.md](references/web_setup.md)
    -   **Android**: See
        [references/android_setup.md](references/android_setup.md)
    -   **iOS**: See [references/ios_setup.md](references/ios_setup.md)

## Common Issues

-   **Login Issues:** If the browser fails to open during the login step, use
    `npx -y firebase-tools@latest login --no-localhost` instead.
-   **Genkit:** If using Genkit, install the skills:

    ```bash
    npx skills add genkit-ai/skills
    ```