Wp Abilities API

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 7.1 core behavior. Server-side Abilities shipped in WordPress 6.9; WordPress 7.0 added the client packages and WP AI Client integration. WordPress 7.1 adds unified public exposure metadata, filtered discovery, a complete execution-filter lifecycle, client-safe JSON Schema preparation, REST collection filters/pagination, and schema-aware run-input coercion. Verify version-sensitive behavior against wp-includes/abilities-api, the WP_REST_Abilities_V1_* controllers, and the abilities script modules.

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.
• Registering client-side admin operations with @wordpress/abilities, or loading server abilities into JS with @wordpress/core-abilities.
• Passing abilities to wp_ai_client_prompt()->using_abilities() or handling WP_AI_Client_Ability_Function_Resolver.
• 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 7.0+ - server-side PHP API plus client-side @wordpress/abilities and @wordpress/core-abilities script modules ship in core. Feature-detect 7.1 additions before using them on 7.0.
2. WordPress 6.9.x - server-side PHP API, registry, REST exposure, and core integration ship in core. Feature-detect the JS packages before relying on them.
3. 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.
4. 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.

For JavaScript, prefer script modules and explicit dependencies. Do not assume a window.wp.abilities global exists.

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(
                'public' => 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+ validates these arguments in WP_Ability::prepare_properties() and WP_Abilities_Registry::register():

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.

Server-side PHP registration accepts exactly two slash-separated segments (myplugin/do-thing). The client-side @wordpress/abilities registry accepts 2-4 segments, but use the two-segment form for abilities that need to round-trip through PHP, REST, or the WP AI Client.

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 normalization, validation, and permission filters/callbacks cheap, deterministic, and side-effect-free. In the REST run flow, WordPress can normalize, validate, and check permissions before dispatch, then WP_Ability::execute() repeats the execution pipeline. Do not put billing, remote calls, writes, or one-shot state in these stages.

Executing an ability from PHP

$ability = wp_get_ability( 'myplugin/site-info' );
if ( $ability instanceof WP_Ability ) {
    $result = $ability->execute(); // This ability has no input_schema.
}

For an ability with a non-empty input_schema, pass the matching normalized input array to execute( $input ).

Public lookup helpers:

• wp_get_ability( string $id ): ?WP_Ability
• wp_get_abilities( array $args = array() ): 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 and JavaScript exposure

On WordPress 7.1, set meta.public = true when the operation is intended for client channels. It defaults show_in_rest to true; an explicit show_in_rest => false overrides it. Set only show_in_rest => true when REST exposure is intended but broader public-channel intent is not. Neither flag grants execution permission.

Core exposes list/get/run routes, enforces the ability permission callback, selects GET/POST/DELETE from annotations, and prepares schemas with wp_prepare_json_schema_for_client(). List requests support bounded pagination, category, namespace, and declared meta filters. Public constraints belong in JSON Schema; PHP callbacks and WordPress-only keywords are removed from client schemas. Read reference.md for route, lifecycle, and filtering details.

Use @wordpress/core-abilities to bridge server abilities into JavaScript and await its exported ready promise before immediate execution. Use @wordpress/abilities alone for client-only categories/abilities. Client-side permission callbacks never replace PHP authorization. Read reference.md for the verified route shapes, module bootstrap, and complete client examples.

WP AI Client integration

WordPress 7.0+ can expose selected server-side abilities as AI model function declarations:

$result = wp_ai_client_prompt( 'Summarize current site diagnostics.' )
    ->using_abilities( 'core/get-site-info', 'core/get-environment-info' )
    ->generate_text_result();

For AI-driven ability execution, instantiate WP_AI_Client_Ability_Function_Resolver with an explicit allowlist. Never give a model a blanket list of all abilities; the ability's own permission_callback still runs, but the resolver allowlist is the first boundary.

MCP adapter — bridging to AI agents

The WordPress team maintains a separate MCP adapter that can bridge eligible Abilities to the Model Context Protocol. Exposure is adapter configuration and metadata dependent; do not assume every registered or merely public Ability becomes an MCP tool. The ability's permission callback remains mandatory.

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

Choose by contract, not novelty: Ability for a discoverable typed operation, REST for an HTTP resource/integration contract, and an action/filter for an in-process extension point.

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.
• Use meta.public and channel flags deliberately on 7.1. public seeds show_in_rest; explicit show_in_rest wins. Exposure never replaces authorization.
• Use @wordpress/core-abilities for server abilities in JS. Use @wordpress/abilities alone only for client-only abilities.
• Prepare schemas before sending them to non-WordPress clients. Use wp_prepare_json_schema_for_client(); allowing a keyword does not add server validation for it.
• Treat 7.1 lifecycle filters as trusted policy code. wp_pre_execute_ability bypasses normalization, validation, permission, callback, output validation, and before/after actions when it short-circuits.
• Allowlist abilities for WP AI Client tool use. Do not pass all registered abilities to a prompt.
• 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

Audit wrong lifecycle hooks, missing categories/schemas/permissions, unconditional permission on privileged writes, empty descriptions, generic namespaces, client categories registered after their abilities, and blanket AI tool allowlists. Corrected examples are in reference.md.

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-ai-client when abilities are being exposed as AI model tools or chained through prompt workflows.
• 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).
• Advanced @wordpress/abilities store internals beyond registration, querying, execution, and unregistering.
• 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. The verified WordPress 7.1 execution lifecycle is summarized in reference.md.

References

• Abilities API documentation — primary authoritative source.
• Introducing the Abilities API (Nov 2025) — announcement post with concrete examples.
• Client-Side Abilities API in WordPress 7.0.
• Abilities API improvements in WordPress 7.1.
• 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.