WordPress Abilities API

A standardized registry for plugin / theme / core functionality, designed primarily so AI agents and external tools can discover what a WordPress site can do and invoke those capabilities through a uniform contract. Each Ability has a stable identifier, JSON-Schema-typed inputs and outputs, and a required permission callback. WP_Ability::execute() validates input, checks permissions, executes, and validates output.

Pre-Abilities, the same functionality was scattered across do_action, apply_filters, custom REST routes, public PHP functions, and ad-hoc plugin APIs (each with its own conventions). The Abilities API consolidates that into one machine-readable surface.

This skill is grounded in WordPress 6.9 core behavior. If a current handbook page and installed core disagree, verify against the target site's wp-includes/abilities-api and REST controller classes before coding.

When to use this skill

Trigger when ANY of the following is true:

• Scaffolding plugin functionality that AI agents (Claude, ChatGPT, custom MCP clients) should be able to discover and invoke.
• Designing an admin tool whose logic should be reachable from BOTH PHP code and the block editor JS without writing two parallel implementations.
• Reviewing a plugin where you see wp_register_ability, wp_get_ability, WP_Ability, the wp_abilities_api_init action, or the @wordpress/abilities JS package.
• Deciding whether to expose a feature as a custom REST endpoint vs an Ability.
• Migrating an existing custom REST endpoint to the Abilities API.

Availability and installation

Three installation paths, depending on WP version:

1. WordPress 6.9+ — server-side PHP API, registry, REST exposure, and core integration ship in core. No additional install needed.
2. WordPress < 6.9 — Composer package for plugins that bundle their own dependencies:

   composer require wordpress/abilities-api
   

   Package: https://packagist.org/packages/wordpress/abilities-api.
3. WordPress < 6.9 — feature plugin for site-wide install: download the latest release ZIP from https://github.com/WordPress/abilities-api or install via WP admin.

The JavaScript client is documented as @wordpress/abilities / wp.abilities, but do not assume the script is registered on every WP 6.9 install. Feature-detect the script handle or call the REST endpoints directly.

Registering a category (prerequisite)

Every Ability MUST belong to a category. Register categories on the dedicated init action (Abilities API docs):

add_action( 'wp_abilities_api_categories_init', 'myplugin_register_ability_categories' );

function myplugin_register_ability_categories(): void {
    wp_register_ability_category(
        'myplugin-site-information',
        array(
            'label'       => __( 'Site Information', 'myplugin' ),
            'description' => __( 'Abilities that report on site state.', 'myplugin' ),
        )
    );
}

If two plugins register the same category slug, the second registration fails with _doing_it_wrong() and returns null; the first category remains registered. Pick a slug specific enough to avoid collisions (myplugin-tools, not tools).

Registering an ability — minimal example

add_action( 'wp_abilities_api_init', 'myplugin_register_abilities' );

function myplugin_register_abilities(): void {
    wp_register_ability(
        'myplugin/site-info',
        array(
            'label'       => __( 'Site Info', 'myplugin' ),
            'description' => __( 'Returns information about this WordPress site.', 'myplugin' ),
            'category'    => 'myplugin-site-information',
            'input_schema'  => array(),
            'output_schema' => array(
                'type'       => 'object',
                'properties' => array(
                    'site_name' => array(
                        'type'        => 'string',
                        'description' => __( 'The name of the site.', 'myplugin' ),
                    ),
                    'php_version' => array(
                        'type'        => 'string',
                        'description' => __( 'PHP version running on the server.', 'myplugin' ),
                    ),
                ),
            ),
            'execute_callback'    => 'myplugin_get_site_info',
            'permission_callback' => static fn () => current_user_can( 'manage_options' ),
            'meta' => array(
                'show_in_rest' => true,
            ),
        )
    );
}

function myplugin_get_site_info(): array {
    return array(
        'site_name'   => get_bloginfo( 'name' ),
        'php_version' => PHP_VERSION,
    );
}

Registration arguments — what's required

WordPress 6.9.4 core validates these arguments in WP_Ability::prepare_properties() and WP_Abilities_Registry::register():

Field	Required	Type	Notes
label	yes	string	Translated, human-readable.
description	yes	string	Translated. AI agents read this to decide whether to invoke.
category	yes	string	Slug must match a registered category.
input_schema	no	array	Required in practice when the ability accepts input. If omitted/empty and input is provided, execution returns ability_missing_input_schema.
output_schema	no in core, yes in docs/review	array	Core allows omission and then skips output validation. Provide it anyway for contracts, REST discovery, and agents.
execute_callback	yes	callable	The PHP function that runs.
permission_callback	yes	callable	Returns true, false, or WP_Error. Enforced by WP_Ability::execute() and by REST run permission checks.
meta	optional	array	Additional metadata. 'show_in_rest' => true exposes the ability via the REST endpoints.

The description is the most important field for AI consumers — it's what an agent reads to decide whether the Ability is the right tool. Write it the way you'd describe the function to a smart colleague reviewing the API.

Callback arity depends on input_schema: if the schema is empty, WordPress calls execute_callback and permission_callback with no arguments. If the schema is non-empty, WordPress passes the normalized input as the first argument.

Naming convention

Ability identifier: namespace/ability-name (slash-separated, kebab-case on both sides).

• The namespace is your plugin slug or a sub-system inside it (myplugin, myplugin-billing).
• The ability-name describes what it does (get-site-info, cancel-subscription, summarize-post).

Pick names a non-developer could read aloud — myplugin/cancel-subscription is better than myplugin/cancel-sub-v2. Treat the identifier as a public API contract: once an Ability is shipped and an AI agent or external client depends on it, renaming is a breaking change.

Permission callback

Required. Return true to allow execution, false to deny, or WP_Error for a structured REST permission failure. WP_Ability::execute() enforces this for direct PHP execution; if the callback returns WP_Error there, core logs it via _doing_it_wrong() and returns a generic ability_invalid_permissions error so the message is not leaked. The REST run endpoint also checks permissions before execution:

'permission_callback' => static function (): bool {
    return current_user_can( 'manage_options' );
},

For object-level abilities (operate on a specific post / user / order), pass the object ID through the meta-capability check:

'permission_callback' => static function ( array $input ): bool {
    return current_user_can( 'edit_post', (int) ( $input['post_id'] ?? 0 ) );
},

Keep permission callbacks cheap and side-effect-free. In the REST run flow, WordPress validates input and calls check_permissions() in the REST permission_callback, then WP_Ability::execute() validates and checks permissions again before running the ability. Do not put logging, billing, remote API calls, or state changes in permission_callback.

Executing an ability from PHP

$ability = wp_get_ability( 'myplugin/site-info' );
if ( $ability instanceof WP_Ability ) {
    $result = $ability->execute( $input ); // $input is the args array matching input_schema
}

Helpers documented in the announcement:

• wp_get_ability( string $id ): ?WP_Ability
• wp_get_abilities(): array<string, WP_Ability>
• wp_has_ability( string $id ): bool

For inspection / debugging during development, use wp shell:

$ wp shell
wp> wp_has_ability( 'myplugin/site-info' );
=> bool(true)
wp> wp_get_ability( 'myplugin/site-info' );
=> object(WP_Ability) ...

REST exposure

When meta.show_in_rest = true, the Ability is automatically exposed under:

• GET /wp-json/wp-abilities/v1/abilities — list all
• GET /wp-json/wp-abilities/v1/abilities/{namespace}/{ability} — get one, where the captured name is namespace/ability
• GET|POST|DELETE /wp-json/wp-abilities/v1/abilities/{namespace}/{ability}/run — execute

This path shape is verified against the WP 6.9.4 core REST controllers. If a handbook page, feature plugin, or bundled Composer package shows a different path shape, inspect WP_REST_Abilities_V1_*_Controller::register_routes() on the target site.

The method is selected from annotations in the WP 6.9.4 run controller: readonly: true expects GET; destructive: true plus idempotent: true expects DELETE; everything else expects POST. The route is registered as ALLMETHODS, but incorrect methods return a 405 error.

The permission_callback is enforced on the REST endpoints automatically; you don't need to write a separate register_rest_route permission check. REST list/get endpoints also require an authenticated user with read.

This is the primary reason to prefer Abilities over custom REST routes for new code: one registration, one permission contract, one schema, and the registry is discoverable.

JavaScript client

const { executeAbility } = window.wp?.abilities ?? {};

if ( executeAbility ) {
    const result = await executeAbility( 'myplugin/site-info', {
        /* input matching input_schema */
    } );
}

The Block Editor handbook documents wp.abilities and @wordpress/abilities, including getAbilities, getAbility, getAbilityCategories, and executeAbility. In plugin code, feature-detect the client or enqueue the script from the package you actually bundle; otherwise call the REST endpoint with apiFetch.

MCP adapter — bridging to AI agents

The WordPress team maintains a separate MCP adapter that bridges the Abilities registry to the Model Context Protocol — the protocol Claude, ChatGPT, and other AI agent runtimes use to discover and invoke external tools. With the adapter installed, every registered Ability becomes an MCP tool the AI can call, gated by the same permission_callback.

Architectural details of the MCP adapter were not included in the Nov 2025 announcement (deferred to a follow-up post). For now, the practical takeaway: registering a clean, well-described Ability also makes it AI-agent-ready without any extra code on your side, IF the site administrator installs the MCP adapter.

When to use an Ability vs a custom REST route vs a custom hook

Situation	Use
Operation that AI agents / external tools should discover and invoke	Ability
Operation called only from your own JS / blocks, with rich validation	Either Ability (preferred) or custom REST route
Internal extension point (other plugins / themes can wire callbacks)	Custom action / filter hook (see wp-plugin-hooks)
Pure UI rendering with no logic to expose externally	Block / shortcode, NOT an Ability
Webhook receiver from a third-party service	Custom REST route — webhooks usually need a fixed URL contract that doesn't fit the Abilities namespace shape

The default in 2026 for new "operation surface" code in a WP plugin is: try as an Ability first.

Critical rules

• Register on wp_abilities_api_init for abilities, wp_abilities_api_categories_init for categories. Don't register on init directly.
• Categories are prerequisite. Register categories before abilities.
• Identifier namespace/ability-name is a public contract — treat it like a versioned API.
• Always provide a permission_callback; core requires it. Use object-aware capability checks for object-scoped abilities.
• Provide schemas even when core does not force them. If the ability accepts input, input_schema is required in practice; without it, provided input is rejected. output_schema is essential for documentation and agents.
• Set meta.show_in_rest = true if external tools should call the ability. Without it, only PHP-side ->execute() works.
• Description is the AI's tool selector. Write it for a reader who doesn't know your plugin.
• For pre-6.9 sites, use the Composer package or feature plugin. Don't reimplement the registry yourself.

Common mistakes

// WRONG — registering on 'init' instead of 'wp_abilities_api_init'
add_action( 'init', function () {
    wp_register_ability( 'myplugin/foo', /* ... */ );
} );

// WRONG — no category registered, ability registration returns null
wp_register_ability( 'myplugin/foo', array(
    'category' => 'never-registered',
    /* ... */
) );

// WRONG — permission_callback always returns true on a write action
'permission_callback' => '__return_true', // anyone with REST access can invoke

// WRONG — empty description; AI agents have nothing to choose against
'description' => '',

// WRONG — ability expects input but has no schema; provided input is rejected
'input_schema'    => array(),
'execute_callback' => function ( array $input ) {
    if ( ! isset( $input['post_id'] ) || ! is_numeric( $input['post_id'] ) ) { /* ... */ }
}
// Should be: declare 'post_id' as a required integer in input_schema. With a
// non-empty input_schema, the callback receives the normalized input.

// WRONG — namespace collision with another plugin
wp_register_ability( 'tools/cancel', /* ... */ ); // generic; collide-prone

// RIGHT — plugin-prefixed namespace
wp_register_ability( 'myplugin/cancel-subscription', /* ... */ );

Cross-references

• Run wp-rest-api when comparing against custom register_rest_route patterns. Many existing custom REST endpoints in plugin codebases would be cleaner as Abilities.
• Run wp-plugin-hooks for the case where the right primitive is actually an apply_filters extension point inside the plugin, not a publicly invocable Ability.
• Run wp-security-audit on the execute_callback — it's a request-handling endpoint reached through REST and MCP. Sanitize / validate inputs, escape outputs, treat the input as untrusted regardless of the schema.

What this skill does NOT cover

• The MCP adapter's internal architecture and configuration (deferred to a separate post in the official series).
• The full @wordpress/abilities JS package API surface beyond basic discovery and execution.
• Multisite-network considerations for Abilities (not addressed in the Nov 2025 announcement; verify before relying on per-site vs network registration semantics).
• WP-CLI command coverage beyond wp shell inspection (no dedicated CLI commands documented yet).
• Building a full hook extension layer around abilities. Core provides wp_abilities_api_categories_init, wp_abilities_api_init, wp_before_execute_ability, wp_after_execute_ability, wp_register_ability_category_args, and wp_register_ability_args.

References

• Abilities API documentation — primary authoritative source.
• Introducing the Abilities API (Nov 2025) — announcement post with concrete examples.
• wordpress/abilities-api Composer package.
• WordPress/abilities-api on GitHub — active feature-plugin repository (the older archived repo is NOT canonical).
• Make WordPress Core AI team blog — ongoing development discussion.