Skill group vs MCP vs plugin
A skill group is an operating profile for local SKILL.md directories.
Use agent-skill-groups when an agent workstation already has many skills and you need a repeatable way to keep only the right scenario profile active.
Comparison
| Concept | What it is | Typical files | Runtime effect |
|---|---|---|---|
| Agent Skill | Instructions and optional assets for one capability. | SKILL.md, references, scripts, assets. | Teaches the agent when and how to use a capability. |
| Skill group | A named scenario profile made from multiple skills. | groups.json. | Emits current-session load/unload packs and can move selected skill directories active or disabled. |
| MCP server | A protocol server that exposes callable tools or resources. | Server code and MCP config. | Gives the agent live tool or resource calls. |
| Plugin | A runtime-specific bundle. | Manifest plus skills, MCP config, or app files. | Installs or exposes capabilities according to that runtime. |
Why Skill Groups Exist
Large skill libraries become noisy when every skill is always active. agent-skill-groups keeps a small core profile active and parks specialized skills in a managed disabled pool.
Loading has two layers. session-load reads a group from active roots or the disabled pool and prints a current-session context pack for the already-running conversation. session-unload prints a stop pack for the same conversation. profile changes filesystem placement only when native runtime discovery should change after a reload, rescan, or new session.
What It Does Not Do
It does not edit skill contents, run MCP servers, or replace a runtime's plugin installer. It manages filesystem placement for skills, can render current-session load/unload packs, and writes an AGENTS.md or CLAUDE.md memory block.
Safe First Test
agent-skill-groups demo --jsonThe demo creates sample active and disabled skill roots, writes groups.json and an agent memory block, switches a profile, restores the backup, and reports ok: true when the workflow succeeds.
Decision Guide
- Use a skill group when the problem is which local skills should be visible for this task.
- Use MCP when the problem is the agent needs to call an external tool or data source.
- Use a plugin when the runtime needs an installable bundle of capabilities.
- Use a plain Agent Skill when the agent needs reusable instructions for one capability.