# Wp Abilities API

> Register WordPress Abilities: machine-readable plugin operations with JSON Schema contracts, required permission callbacks, optional REST exposure, client-side abilities, and AI/MCP-friendly discovery. Covers categories, wp_register_ability, WP_Ability::execute, REST run endpoints, @wordpress/abilities, @wordpress/core-abilities, meta.public/show_in_rest, filtered discovery, execution lifecycle hooks, client-safe schemas, annotations, and Ability vs REST route vs custom hook decisions. Use when exposing plugin functionality to agents, admin JS, external tools, WP AI Client workflows, or reviewing AI integration code.

- Skill: `lonsdale201/wp-abilities-api` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add lonsdale201/wp-abilities-api`
- Raw SKILL.md: https://api.skillmd.com/api/skills/lonsdale201/wp-abilities-api/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Product & Planning
- Author: Lonsdale201 (https://skillmd.com/u/lonsdale201)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/lonsdale201/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:
   ```bash
   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](https://developer.wordpress.org/apis/abilities-api/)):

```php
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

```php
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()`:

| 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 | Annotations and exposure flags. In 7.1, `public` seeds channel defaults; explicit `show_in_rest` wins for REST. |

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:

```php
'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:

```php
'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

```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:

```php
$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](https://modelcontextprotocol.io/). 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

| Situation | Use |
|---|---|
| Operation that AI agents / external tools should discover and invoke | **Ability** |
| Typed operation called from your own JS and potentially reusable by tools | Ability |
| Resource CRUD/public headless API with stable HTTP semantics | Custom REST route/controller |
| 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 |

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](https://developer.wordpress.org/apis/abilities-api/) — primary authoritative source.
- [Introducing the Abilities API (Nov 2025)](https://developer.wordpress.org/news/2025/11/introducing-the-wordpress-abilities-api/) — announcement post with concrete examples.
- [Client-Side Abilities API in WordPress 7.0](https://make.wordpress.org/core/2026/03/24/client-side-abilities-api-in-wordpress-7-0/).
- [Abilities API improvements in WordPress 7.1](https://make.wordpress.org/core/2026/07/31/abilities-api-improvements-in-wordpress-7-1/).
- [`wordpress/abilities-api` Composer package](https://packagist.org/packages/wordpress/abilities-api).
- [WordPress/abilities-api on GitHub](https://github.com/WordPress/abilities-api) — active feature-plugin repository (the older archived repo is NOT canonical).
- [Make WordPress Core AI team blog](https://make.wordpress.org/ai/) — ongoing development discussion.