Add content-reading abilities for WordPress posts/pages

[bradvin]

Problem

The agent can currently read/write workspace and memory, but cannot inspect core WordPress content entities (posts/pages) through dedicated read abilities. This limits useful site-aware assistance.

Current State

• Built-in abilities are registered under includes/abilities/ and exposed through Abilities_Helper.
• Existing model tool flow already supports paginated/structured outputs and policy checks.

Implementation Plan

1) Add read-only content abilities

Create new built-in abilities under includes/abilities/:

• post_list (list posts with filters)
• post_read (read a single post/page by ID or slug)

2) Input schema (strict)

For post_list:

• post_type (post, page initially)
• status (default safe statuses)
• search
• author
• per_page (bounded, e.g. 1-50)
• page
• orderby, order

For post_read:

• one of id or slug
• optional post_type

3) Output schema (model-friendly)

Return concise structured payload:

• id, type, status, slug, title, excerpt, content (optionally truncated), date fields, author info, link.
• Include pagination metadata for list endpoint.

4) Capability and policy

• Use read-level permission callbacks (current_user_can( 'read' )) plus runtime policy gates in Abilities_Helper.
• Mark as readonly in ability annotations.

5) Register + map

• Register abilities in includes/class-abilities.php.
• Add tool mapping in Abilities_Helper::TOOL_TO_ABILITY.

Acceptance Criteria

• Agent can list and read posts/pages via tool calls.
• Inputs are validated and bounded; invalid filters fail gracefully.
• Outputs are deterministic and stable across repeated calls.
• No write/delete behavior introduced.

Test Plan

• Unit tests for ability callbacks:
  • list paging/filter behavior,
  • read by ID/slug,
  • invalid inputs.
• Unit tests for tool declaration registration and mapping.
• Permission tests (denied vs allowed paths).

Out of Scope

• Editing/publishing/deleting content.
• Full taxonomy/media traversal in this first pass.