[helloeve]

Adds a decision log for the Progressive Disclosure via Groups SEP, recording four naming and shape decisions reached by the WG.

Motivation and Context

This doc captures the decisions so they're easy to cite and don't get re-litigated. It records four decisions:

1. Keep group as the primitive name — no alternative (Bundles, Collections) is strongly preferable, so there's no reason to churn the established name.
2. Operations are group/get and group/list, and they are stateless — read-only retrieval verbs, rejecting activate/load, which would imply a server-side state transition.
3. "When to use" is the description field — reuses the base-protocol convention instead of summary/selectionGuidance/usage, with content scoped to when to use a group, not how.
4. Optional instructions, with the group's primitives next to it — instructions carries the "how", kept distinct from description; primitives are delivered inline in the same group/get response to keep the shape flat and avoid another nested structure.

How Has This Been Tested?

N/A — documentation only. No code changes.

Breaking Changes

None. This is a decision log and introduces no protocol or code changes.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed