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Plugin Author Guide

This guide explains how to create plugin packages for the babysitter SDK. A babysitter plugin is not a conventional software plugin. Instead, it is a version-managed package of contextual instructions that an AI agent reads and executes to install, uninstall, configure, or migrate between versions of a tool or integration.

Concepts​

  • Plugin package -- A directory within a marketplace repository containing instruction files and optional babysitter process files.
  • Marketplace -- A Git repository with a marketplace.json manifest that indexes available plugins.
  • Registry -- A local JSON file (plugin-registry.json) that tracks which plugins are installed and at what version.
  • Scope -- Plugins can be installed at global scope (~/.babysitter/) or project scope (<projectDir>/.babysitter/).

Plugin Package Directory Structure​

A plugin package is a directory with the following layout:

my-plugin/
  install.md              # Agent-readable installation instructions
  uninstall.md            # Agent-readable uninstallation instructions
  configure.md            # Agent-readable configuration instructions
  install-process.js      # Optional babysitter process for automated install
  uninstall-process.js    # Optional babysitter process for automated uninstall
  configure-process.js    # Optional babysitter process for automated configuration
  migrations/             # Version migration files
    1.0.0_to_1.1.0.md
    1.1.0_to_1.2.0.md
    1.2.0_to_2.0.0.js

All files are optional. The SDK reads whichever files are present and returns their content to the agent.

Writing install.md​

The install.md file contains markdown instructions that an AI agent reads and follows to install the plugin into a project or user environment. Write the instructions as if speaking to a capable developer agent.

Guidelines:

  • Use numbered steps for sequential operations.
  • Be explicit about file paths, configuration keys, and expected values.
  • Reference environment-specific locations using placeholders like <project-root> or <home-dir>.
  • If the install requires running a babysitter process, note that the process file is install-process.js in the same directory.
  • Include any prerequisites (required tools, environment variables, permissions).

Example install.md​

# Install my-plugin

## Prerequisites
- Node.js 18 or later
- Access to the project's `.claude/settings.json`

## Steps

1. Add the plugin entry to `.claude/settings.json` under the `permissions.allow` array:
   ```json
   {
     "permissions": {
       "allow": ["my-plugin@my-org"]
     }
   }

  1. Create the configuration directory:

    mkdir -p .a5c/plugins/my-plugin

  2. Copy the default configuration:

    cp <plugin-package-dir>/defaults/config.json .a5c/plugins/my-plugin/config.json

  3. Run the install process for automated setup:

    • The babysitter process file install-process.js in this directory handles remaining setup steps including API key validation.

## Writing uninstall.md

The `uninstall.md` file contains instructions for removing the plugin. It should reverse the steps performed during installation.

### Example uninstall.md

```markdown
# Uninstall my-plugin

1. Remove the plugin entry from `.claude/settings.json` under `permissions.allow`.
2. Delete the plugin configuration directory:

rm -rf .a5c/plugins/my-plugin

3. Remove any environment variables set during installation.

Writing configure.md​

The configure.md file contains instructions for configuring or reconfiguring the plugin after installation. This is useful for changing settings, updating API keys, or adjusting plugin behavior.

Example configure.md​

# Configure my-plugin

## Available Settings

| Setting | Default | Description |
|---------|---------|-------------|
| `apiKey` | (none) | API key for the external service |
| `timeout` | `30000` | Request timeout in milliseconds |
| `logLevel` | `info` | Logging verbosity (debug, info, warn, error) |

## Steps

1. Open `.a5c/plugins/my-plugin/config.json`
2. Update the desired settings
3. Validate the configuration by running:

babysitter health --json

Babysitter Process Files​

Process files (install-process.js, uninstall-process.js, configure-process.js) are standard babysitter process definitions. They export an async function process(inputs, ctx) and use defineTask to define steps that the orchestrator executes.

These process files enable automated, multi-step operations that go beyond what static markdown instructions can describe. Common uses:

  • Validating external service connectivity
  • Running database migrations
  • Generating configuration files from templates
  • Performing health checks after installation

The SDK detects process files by checking for their existence at conventional paths within the plugin package directory. When present, the processFile field in the command output contains the absolute path to the file.

Creating Migration Files​

Migration files live in the migrations/ subdirectory of the plugin package. They describe how to move from one version to another.

Naming Convention​

<fromVersion>_to_<toVersion>.<ext>

Where:

  • <fromVersion> -- The source version (semver with dots, dashes, and pre-release identifiers allowed)
  • <toVersion> -- The target version
  • <ext> -- Either md (markdown instructions) or js (babysitter process file)

Examples:

1.0.0_to_1.1.0.md
1.1.0_to_1.2.0.md
1.2.0_to_2.0.0.js
2.0.0-beta_to_2.0.0.md

Markdown Migration Files (.md)​

Contain agent-readable instructions for performing the migration:

# Migration from 1.0.0 to 1.1.0

## Breaking Changes
- The `timeout` config key has moved from top-level to `settings.timeout`

## Steps

1. Open `.a5c/plugins/my-plugin/config.json`
2. Move the `timeout` value:
   - Remove `"timeout": <value>` from the top level
   - Add `"settings": { "timeout": <value> }` if the `settings` key does not exist
3. Verify the configuration is valid by running `babysitter health`

JavaScript Migration Files (.js)​

Standard babysitter process files that automate the migration. The SDK returns the absolute path to the file in the processFile field so the agent can execute it.

Example Complete Plugin Package​

example-plugin/
  install.md
  uninstall.md
  configure.md
  install-process.js
  migrations/
    1.0.0_to_1.1.0.md
    1.1.0_to_2.0.0.md
    2.0.0_to_2.1.0.js

With a corresponding marketplace.json entry:

{
  "name": "example-plugin",
  "description": "An example babysitter plugin",
  "latestVersion": "2.1.0",
  "versions": ["2.1.0", "2.0.0", "1.1.0", "1.0.0"],
  "packagePath": "plugins/example-plugin",
  "tags": ["example", "tutorial"],
  "author": "my-org"
}

Plugin Lifecycle​

The complete lifecycle for a plugin from the agent's perspective:

  1. Discovery -- plugin:list-plugins to browse available plugins in a marketplace.
  2. Install -- plugin:install returns instructions from install.md. Agent executes them. Then plugin:update-registry records the version.
  3. Configure -- plugin:configure returns instructions from configure.md. Agent executes them.
  4. Update -- plugin:update resolves the migration chain and returns ordered migration instructions. Agent executes each migration step. Then plugin:update-registry records the new version.
  5. Uninstall -- plugin:uninstall returns instructions from uninstall.md. Agent executes them. Then plugin:remove-from-registry cleans up the registry.