WP Abilities API

When to use

Use this skill when the task involves:

• registering abilities or ability categories in PHP,
• exposing abilities to clients via REST (wp-abilities/v1),
• consuming abilities in JS (notably @wordpress/abilities),
• diagnosing “ability doesn’t show up” / “client can’t see ability” / “REST returns empty”.

Inputs required

• Repo root (run wp-project-triage first if you haven’t).
• Target WordPress version(s) and whether this is WP core or a plugin/theme.
• Where the change should live (plugin vs theme vs mu-plugin).

Procedure

Before deciding what to register, read references/domain-vs-projection.md — abilities live at the domain capability layer; MCP / Command Palette / REST exposure is a projection. Registration shape and exposure shape are different decisions, and conflating them forces re-registration every time a consumer's constraints change.

1) Confirm availability and version constraints

• If this is WP core work, check signals.isWpCoreCheckout and versions.wordpress.core.
• If the project targets WP < 6.9, you may need the Abilities API plugin/package rather than relying on core.

2) Find existing Abilities usage

Search for these in the repo:

• wp_register_ability(
• wp_register_ability_category(
• wp_abilities_api_init
• wp_abilities_api_categories_init
• wp-abilities/v1
• @wordpress/abilities

If none exist, decide whether you’re introducing Abilities API fresh (new registrations + client consumption) or only consuming.

3) Register categories (optional)

If you need a logical grouping, register an ability category early (see references/php-registration.md).

4) Register abilities (PHP)

For grouping decisions (how many abilities to register, and where to put filters vs. new ability names), read references/grouping-heuristic.md first — it keeps you from shipping one atomic ability per REST operation.

To avoid drift between the ability and the existing UI / REST code path, see references/shared-core-service.md — abilities, REST handlers, CLI commands, and UI controllers should be thin adapters over a shared service. The reference also covers the metric trap (REST handlers that emit usage telemetry) and the AGENTS.md rule for keeping registrations in sync when underlying code paths change.

For shared helper patterns when multiple execute callbacks delegate to existing REST controllers, see references/plugin-family-patterns.md (identify the shared-API-client vs zero-arg-controllers shape) and references/delegate-helper-pattern.md (one helper shape that works, and when not to use it).

For standardized WP_Error codes that let agents reason about retry vs. escalation, see references/error-code-vocabulary.md.

Implement the ability in PHP registration with:

• stable id (namespaced),
• label/description,
• category,
• meta:
• add readonly: true when the ability is informational,
• set show_in_rest: true for abilities you want visible to clients.

Use the documented init hooks for Abilities API registration so they load at the right time (see references/php-registration.md).

5) Confirm REST exposure

• Verify the REST endpoints exist and return expected results (see references/rest-api.md).
• If the client still can’t see the ability, confirm meta.show_in_rest is enabled and you’re querying the right endpoint.

6) Consume from JS (if needed)

• Prefer @wordpress/abilities APIs for client-side access and checks.
• Ensure build tooling includes the dependency and the project’s build pipeline bundles it.

Verification

• wp-project-triage indicates signals.usesAbilitiesApi: true after your change (if applicable).
• REST check (in a WP environment): endpoints under wp-abilities/v1 return your ability and category when expected.
• If the repo has tests, add/update coverage near:
• PHP: ability registration and meta exposure
• JS: ability consumption and UI gating

Failure modes / debugging

• Ability never appears:
• registration code not running (wrong hook / file not loaded),
• missing meta.show_in_rest,
• incorrect category/ID mismatch.
• REST shows ability but JS doesn’t:
• wrong REST base/namespace,
• JS dependency not bundled,
• caching (object/page caches) masking changes.
• Execute callback returns unexpected errors or silently ignores input:
• input_schema defaults aren't being applied, pagination key drift between the ability and the backing, or empty()-based ID validation — see references/input-schema-gotchas.md.

Escalation

• If you’re uncertain about version support, confirm target WP core versions and whether Abilities API is expected from core or as a plugin.
• For canonical details, consult:
• references/rest-api.md
• references/php-registration.md