Relations

->relations(['comments']) exposes a read only tool for the relation, list_post_comments in this example:

McpResource::make(PostResource::class)
    ->crud()
    ->relations(['comments'])

The related model has to be an MCP resource on the same panel. That's what supplies the field visibility, read transformations and policy the related records are served through, so reading them here requires exactly what list_comments requires, and the relation is scoped to that resource's own query.

A relation whose model is not exposed produces no tool at all, so a public parent can never become a way to read a private table.

Writing through a relation

Relation tools can't write yet. The one relationship an agent can change is a BelongsToMany exposed on the form as a multiple relationship Select, which is synced to exactly the set of keys it sends. See relationship selects.