[Feature Request] Cross-plugin skill references with namespace syntax

Feature Request: Cross-Plugin Skill Reference for Agents

Summary

Allow agents defined in Plugin A to use skills defined in Plugin B through explicit namespace syntax.

Current Limitation

Currently, the skills field in agents.md only supports referencing skills within the same plugin. There is no way for an agent to load or invoke skills from other installed plugins.

Proposed Solution

Introduce a namespaced syntax for cross-plugin skill references:

# Plugin A: agents/my-agent.md
---
name: my-agent
description: Agent that uses skills from multiple plugins
skills:
  - local-skill              # same plugin
  - plugin-b:external-skill  # from plugin-b
  - plugin-c:another-skill   # from plugin-c
---

Scope Consideration

Even if this feature is limited to plugins within the same marketplace, it would still be highly valuable. This would:

• Maintain security boundaries (only trusted, curated plugins can interact)
• Enable plugin authors in the same marketplace to build complementary, composable tools
• Reduce complexity compared to allowing arbitrary cross-plugin references

Use Cases

1. Modular Plugin Ecosystem: Separate concerns into focused plugins (e.g., research-plugin, writing-plugin, review-plugin) while allowing agents to compose workflows across them.
2. Shared Utility Skills: Create a "common-skills" plugin with reusable skills (formatting, validation, etc.) that any agent from any plugin can use.
3. Domain-Specific Workflows: An orchestrating agent in one plugin can leverage specialized skills from domain-specific plugins without code duplication.

Example Scenario

I have separate plugins for a research-writing pipeline:

• research-plugin: agents for gathering and analyzing information
• writing-plugin: skills for document formatting, structuring, and styling

I want a research-plugin:researcher agent to use writing-plugin:format-document skill to produce well-formatted output, but this is currently impossible without merging plugins.

Additional Considerations

• Dependency declaration in plugin.json (optional/required plugins)
• Graceful handling when referenced plugin is not installed
• Clear error messages for missing cross-plugin dependencies

Thank you for considering this feature\!