Agent MCP, Skill, and Plugin Configuration

MCP servers, Skills, and Plugins extend what an Agent can do. Configure them when creating or updating an Agent to give it external services, domain procedures, and packaged extensions.

The Role of Extensions

The selected Agent program supplies its own native tools, such as reading files, editing code, running commands, and searching. AstraBox does not duplicate those tools in a separate tools field.

Agent configuration adds three kinds of extension:

• MCP servers expose live functions and data.
• Skills provide reusable instructions, procedures, and supporting files.
• Plugins package Skills, commands, and MCP definitions together.

When AstraBox first prepares or rebuilds a Session runtime, it prepares the configured extensions in the sandbox. The Agent program decides when to use them based on the task.

Available Extensions

MCP servers use one of two connections: a remote HTTP service outside the sandbox, or a local stdio command inside it. Connection type and configuration source are separate choices. An Administrator-managed remote MCP server is still remote; administrator management changes who maintains its definition.

Extension	Purpose	Typical scenarios
Remote MCP server	Call an MCP service running outside the Session sandbox	Databases, ticketing systems, document services, internal APIs
Local stdio MCP server	Start an MCP command inside the Session sandbox	Filesystem tools, local analyzers, command-based integrations
Skill	Supply a focused procedure and supporting files	Code review, release checks, report generation
Plugin	Install a reviewed bundle of Skills, commands, and MCP definitions	Team extension packs and domain workflows

Notes:

• A server outside the sandbox is a remote MCP server whether its definition is saved on the Agent, managed by an administrator, or packaged in a Plugin. Those choices change only who maintains the configuration.
• The selected Agent program determines which extension formats it supports. AstraBox rejects an Agent configuration that its selected program does not consume.
• Saving an Agent does not reconfigure a task already running. AstraBox uses the latest extension configuration when it first prepares or rebuilds a Session runtime.
• Network rules and credentials are separate from an MCP definition. A remote server must be reachable from the sandbox, and protected credentials must match its exact destination.

Native and Browser Capabilities

Browser and web capabilities belong to the selected Agent program or to an extension it supports. AstraBox does not define a second platform-level browser toolset with its own tool names.

Use the Agent program's native configuration when it includes browser support. Otherwise, add a browser MCP server or reviewed Plugin and allow its remote and package hosts in the Environment's network policy.

When integrating browser capabilities:

• use the names and permission rules defined by the Agent program or MCP server;
• changing the Agent does not alter a task already running; AstraBox uses the latest settings when it next prepares or rebuilds the Session runtime;
• verify one real browser operation and any live-preview path the extension provides;
• do not assume another Agent program implements the same browser behavior.

Current Formats

Agent-level extensions use the native formats supported by the selected Agent program. Open Console > Agents, create or open an Agent, then use the MCP, Skills, and repositories section.

For an existing Agent, the MCP servers and Skills card also lets you select administrator-managed remote MCP servers and Skills. The direct configuration fields use these formats:

{
  "mcp_servers": {
    "public-data": {
      "type": "http",
      "url": "https://mcp.example.com/mcp"
    }
  },
  "skills": [
    "https://github.com/example/agent-skills.git@REVIEWED_COMMIT_SHA#skills/code-review"
  ],
  "plugin_repos": [
    {
      "url": "https://github.com/example/agent-plugins.git",
      "sha": "REVIEWED_COMMIT_SHA",
      "plugin_paths": ["plugins/code-review"]
    }
  ]
}

The system prompt and every extension are optional. Configure only the capabilities the Agent needs, then click Create or Save.

Extension Configuration Examples

Minimal Configuration (Remote MCP Only)

{
  "mcp_servers": {
    "public-data": {
      "type": "http",
      "url": "https://mcp.example.com/mcp"
    }
  }
}

Full Development Environment

{
  "mcp_servers": {
    "workspace-files": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/workspace"]
    },
    "public-data": {
      "type": "http",
      "url": "https://mcp.example.com/mcp"
    }
  },
  "skills": [
    "https://github.com/example/agent-skills.git@REVIEWED_COMMIT_SHA#skills/code-review"
  ],
  "plugin_repos": [
    {
      "url": "https://github.com/example/agent-plugins.git",
      "sha": "REVIEWED_COMMIT_SHA",
      "plugin_paths": ["plugins/development"]
    }
  ]
}

Update an Agent

Open the Agent in Console > Agents. Change the selected MCP servers or Skills in the extension card, or edit the direct MCP, Skill, and Plugin repository fields, then click Save for that section.

note

Saving does not reconfigure a task already running. AstraBox uses the latest saved Agent when it first prepares or rebuilds a Session runtime. If another user saves the same Agent first, the console reports a conflict instead of overwriting that change.

View the Current Extension Configuration

Open the Agent in Console > Agents. Administrator-managed MCP servers and Skills appear in the MCP servers and Skills card. Direct MCP definitions, Skill sources, and Plugin repositories appear in the MCP, Skills, and repositories section.

FAQ

Q: What happens if I do not configure extensions?

A: The Agent program retains its native tools. It simply has no additional MCP servers, Skills, or Plugins configured on the Agent.

Q: Can extension configuration be overridden at the Session level?

A: Not currently. Extension configuration belongs to the Agent. AstraBox resolves the current Agent configuration when it first prepares or rebuilds a Session runtime. Use another Agent when a different extension set is required.

Q: Does the order of extension entries matter?

A: The Agent program decides when to use an extension based on the task. Names must be unique where the program addresses an extension by name.

Q: Will extension formats change over time?

A: The format belongs to the Agent program, MCP protocol, Skill specification, or Plugin format. Pin reviewed Git revisions and follow the corresponding upstream release notes.