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# Knowledge class

The `Knowledge` class holds pages and notes, declares which scopes exist and who gets which role on them, and gives attached agents the Knowledge tools. See [Knowledge](https://mastra.ai/docs/knowledge/overview) for what it does and a quickstart.

> **Alpha:** Knowledge is in alpha. Its API may change between releases.

## Usage example

```typescript
import { Knowledge, knowledgeMemoryScopes } from '@mastra/core/knowledge'
import { LibSQLStore } from '@mastra/libsql'

export const knowledge = new Knowledge({
  id: 'company',
  storage: new LibSQLStore({ id: 'knowledge', url: 'file:./knowledge.db' }),
  tools: true,
  scopes: {
    ...knowledgeMemoryScopes(),
    'team:$orgId:$teamId': {
      access: [
        { principal: 'self', role: 'editor' },
        { principal: 'org:$orgId', role: 'viewer' },
      ],
    },
  },
})
```

## Constructor options

**scopes** (`KnowledgeScopeDeclarations`): Scope types and concrete scopes this Knowledge knows, keyed by pattern (team:$orgId:$teamId) or address (org:acme). Required. Every run scope of an attached agent must match a declaration. Spread knowledgeMemoryScopes() for Memory's scopes, or pass {} to declare none. See Scope declarations for the fields of each declaration.

**id** (`string`): Identifier. Random if omitted.

**name** (`string`): Name used in logs. Defaults to id.

**description** (`string`): Stored as knowledge.description. Agents and Studio don't use it yet.

**storage** (`MastraCompositeStore`): Storage adapter. Without it, Knowledge uses the storage of the Mastra instance it is registered on.

**tools** (`boolean | { read?: boolean | { maxTokens?: number }; write?: boolean }`): Tools an attached agent gets. true gives all five: knowledge_list, knowledge_search, knowledge_read, knowledge_page and knowledge_note. { read: true } gives the first three. { write: true } gives the last two. { read: { maxTokens } } turns on read and caps each knowledge_read body or match result, and each knowledge_list result, at maxTokens: 1,000 by default, at least 100. See Read pages. (Default: `false`)

**pinnedContext** (`boolean | { maxPins?: number; maxTokens?: number }`): Pinned pages delivered to an attached agent every turn, plus the knowledge_pin tool. Needs Memory. maxPins defaults to 20 and maxTokens to 500, with no maximum. See Pinned context. (Default: `false`)

**vector** (`MastraVector`): Vector store for semantic search. Pass with embedder; passing only one throws. Without both, search is keyword only.

**embedder** (`MastraEmbeddingModel<string>`): Embedding model for semantic search. Pass with vector.

**embedderOptions** (`MastraEmbeddingOptions`): Options passed to the embedder on every call: maxRetries, headers, providerOptions, telemetry.

**instructions** (`false | string | ((parts: { read: string; write: string; pins: string }) => string)`): Replaces the built-in usage instructions added when Knowledge attaches tools. false adds none. A function receives the built-in parts, with an empty string for each disabled group, and must return the same text for the same input so the prompt stays cacheable. See Tool instructions.

The constructor throws a `KnowledgeDeclarationError` when `scopes` is missing or a declaration is invalid, for example two patterns of one type that overlap or a rule principal that doesn't bind. Without `scopes` the message is:

```text
Knowledge needs `scopes`: declare the scopes its runs hold, e.g. `scopes: { ...knowledgeMemoryScopes() }`, or `{}` for none.
```

## Methods

### Tools

#### `createTools()`

```typescript
createTools(options?: { read?: boolean; write?: boolean; pinnedContext?: boolean }): Record<string, Tool>
```

Returns the Knowledge tools for explicit wiring, such as an agent that isn't attached with `knowledge`. Each option overrides the matching group set on the instance, and an omitted option keeps it. On an instance with `pinnedContext` on, `createTools({ write: false })` also returns `knowledge_pin`. See [Knowledge tools](https://mastra.ai/reference/knowledge/knowledge-tools).

```typescript
const tools = knowledge.createTools({ write: false })
// knowledge_list, knowledge_search, knowledge_read
```

#### `getInstructions()`

```typescript
getInstructions(options?: { read?: boolean; write?: boolean; pinnedContext?: boolean }): string
```

Returns the usage instructions that go with `createTools(options)`, built the same way as for an attached agent: the built-in parts for the enabled groups, or what the `instructions` option makes of them.

### Access

#### `explainAccess()`

```typescript
explainAccess(
  runScopes: readonly string[],
  target: { scope: string } | { page: string },
): Promise<KnowledgeAccessExplanation>
```

Explains why a run holding `runScopes` can or can't reach a scope or page. `runScopes` are raw run scopes, as you'd pass to an agent. `target.page` takes a page ID or a page path such as `org:acme#policies/refund`.

```typescript
await knowledge.explainAccess(['org:acme'], { page: 'team:acme:support#refunds' })
// {
//   role: 'viewer',
//   reasons: [{ principal: 'org:acme', role: 'viewer', rule: 'team:$orgId:$teamId', via: 'rule' }],
//   page: { id: '…', scope: 'team:acme:support' },
// }

await knowledge.explainAccess(['org:globex'], { page: 'team:acme:support#refunds' })
// { role: null, reasons: [], page: { id: '…', scope: 'team:acme:support' }, reason: 'hidden' }
```

**role** (`'viewer' | 'contributor' | 'editor' | 'owner' | null`): The strongest role the run has on the target scope. null when it can't read it.

**reasons** (`Array<{ principal: string; role: string; rule: string; via: "self" | "rule" | "belongsTo" }>`): Every rule that gives one of the run's scopes a role there: the held scope, the role, the declaration key or concrete address, and how the rule bound.

**page** (`{ id: string; scope: string }`): The resolved page and its home scope, for page targets that exist.

**reason** (`'missing' | 'hidden' | 'no-rule'`): missing: no such page. hidden: the page exists but the run can't read its scope. no-rule: no rule gives the run a role on the scope.

A run scope with no declaration throws, as it does at run start:

```text
Knowledge run scope "project:x" does not match a declared scope type. Declare it in Knowledge `scopes` (for Memory's resource:/thread: scopes, spread `...knowledgeMemoryScopes()`).
```

A `target.scope` with no declaration throws `Knowledge scope "project:x" does not match a declared scope type.`

> **Warning:** `explainAccess()` is host-only. It tells a missing page from a hidden one, which runs must never learn. Don't expose it through an agent tool, or through a server route without admin-level auth.

#### `readScopeFor()`

```typescript
readScopeFor(principals: readonly string[]): Promise<KnowledgeReadScope>
```

Returns what a holder of `principals` can read: the principals themselves plus every scope their rules give them a role on. Roles don't carry over to further scopes. Pass the result as `read` to the store's read methods when host code reads Knowledge for a user. Undeclared principals throw `Knowledge run scope "project:x" does not match a declared scope type.` An empty list reads nothing.

#### `scopeGrants()`

```typescript
scopeGrants(scope: { address: string; parentAddress?: string | null }): KnowledgeScopeGrant[]
```

The roles the declarations give other scopes on this one, as `{ principal, role }` with the strongest role per principal and `self` rules left out. It reads no storage. `parentAddress` supplies the tree parent that rules binding through `belongsTo` need. Use it for a browsing UI that draws access between scopes. Use `explainAccess()` for one run's view.

#### `scopeDeclaration()`

```typescript
scopeDeclaration(key: string): KnowledgeScopeDeclarationInfo | undefined
```

Returns the declaration a scope was created from, by its declaration key, for display: `{ key, description?, displayLabel?, belongsTo?, children }`. Child keys work too, such as `org:$orgId/private`. Access rules are left out. Use `explainAccess()` for those. Returns `undefined` for an unknown key.

#### `scopeLabel()`

```typescript
scopeLabel(address: string): string | undefined
```

Returns the `displayLabel` for a scope address with its `$params` filled in: `'$orgId organization'` on `org:$orgId` gives `acme organization` for `org:acme`. A concrete address's own `displayLabel` wins. Returns `undefined` when the address matches no declaration or has no label.

### Host writes

`upsertPage()`, `removePage()`, `addNote()`, `updateNote()` and `removeNote()` are host-only: they check no run scopes or access rules. Don't expose them through an agent tool, or through a server route without admin-level auth.

#### `upsertPage()`

```typescript
upsertPage(input: {
  scope: string
  path: string
  name: string
  description?: string
  body?: string
  author?: string
}): Promise<{ page: KnowledgePage; status: 'created' | 'updated' | 'unchanged' }>
```

Creates or updates the page at `path` (keys joined by `/`, such as `guides/install`) in `scope`, creating the scope and any missing pages along the path. Writing the same path again updates that page. `description` and `body` keep their stored values when left out. An `unchanged` result means nothing was written. The page keeps its version, emits no change event and isn't re-embedded. `author` is recorded as the writer and defaults to `host`. A path with no keys throws `Knowledge page path "<path>" needs at least one key.` See [Load your content](https://mastra.ai/docs/knowledge/load-your-content).

#### `removePage()`

```typescript
removePage(input: { scope: string; path: string; author?: string }): Promise<KnowledgePage | null>
```

Removes the page at `path` and resolves to it, or to `null` when no page is there. Throws `"<scope>#<path>" has child pages; remove them first.` for a page with children, and `"<scope>#<path>" is declared in config; change the scope's pages to remove it.` for a template page. Throws without retrying when another write changed the page first.

#### `addNote()`

```typescript
addNote(input: {
  scope: string
  path: string
  text: string
  when?: Date
  stamps?: string[]
  author?: string
}): Promise<KnowledgeNote>
```

Adds a note to the page at `path`. `text` is at most 250 tokens. `[[scope#path]]` mentions of existing pages link the note to them. Other `[[...]]` text stays plain. `stamps` are the scope addresses whose readers see the note and default to the page's scope. Throws `KnowledgeNotFoundError` when the page doesn't exist.

#### `updateNote()`

```typescript
updateNote(input: { id: string; text: string; when?: Date; stamps?: string[]; author?: string }): Promise<KnowledgeNote>
```

Replaces a note: adds the new note, then removes the old one, and resolves to the new note with a new ID. `when` and `stamps` keep their old values when left out or empty. If removing the old note fails after the add, both notes exist and the call throws, so remove the one you don't want. When the old note was already removed by someone else, the new note is removed too and nothing is left behind.

#### `removeNote()`

```typescript
removeNote(input: { id: string; author?: string }): Promise<KnowledgeNote | null>
```

Removes a note and resolves to it, or to `null` when it's already gone.

### Storage and maintenance

#### `getStorage()`

```typescript
getStorage(): Promise<KnowledgeStorage>
```

Returns the Knowledge store, for host code such as admin pages, deletes and your own import scripts. Its read methods take `read`: `'all'` skips the role checks, so pass the value from `readScopeFor()` whenever a read should be limited to what a user can see.

```typescript
const store = await knowledge.getStorage()
const read = await knowledge.readScopeFor(['org:acme'])
const [scope] = await store.getScopesByAddress(['team:acme:support'])
const page = await store.getPageByPath({ scopeId: scope.id, path: ['handbook', 'refunds'], read })
```

#### `reindexLinks()`

```typescript
reindexLinks(): Promise<number>
```

Rebuilds the page link index from every page body, and resolves to how many pages it indexed. Writes keep the index current, so this is for pages that predate it or were written straight to the store. It needs no vector store.

#### `renameScopeDeclaration()`

```typescript
renameScopeDeclaration(from: string, to: string): Promise<number>
```

Moves stored scopes created from declaration key `from`, and its child scopes (`from/<name>`), to key `to`, in one step. Resolves to how many scopes moved. Refuses, and changes nothing, when `from` is still in `scopes`, `to` isn't, or a stored address doesn't match `to`'s pattern. Until stored keys match `scopes`, the instance refuses to run.

On MongoDB, the rename runs in a transaction only on a replica set. On a standalone server it isn't atomic, and a failure partway can leave some scopes renamed.

See [rename or retire a scope type](https://mastra.ai/reference/knowledge/scope-declarations).

### Events

#### `onChange()`

```typescript
onChange(listener: (event: KnowledgeChangeEvent) => void): () => void
```

Calls `listener` after each committed write made through this instance's store: tool writes, host writes through `getStorage()`, and new scopes. Returns a function that removes the listener. Use it to refresh a live UI. Writes made on a store obtained another way aren't seen.

Events carry IDs, not content or access, so anything that relays them to people must re-read each page under that person's read scope from `readScopeFor()`:

| `kind`  | `op`                                          | Fields                                                                                                   |
| ------- | --------------------------------------------- | -------------------------------------------------------------------------------------------------------- |
| `scope` | `create`                                      | `pageId`, `scopeId` (the new scope page's ID)                                                            |
| `page`  | `create`, `update`, `move`, `merge`, `delete` | `pageId`, `scopeId`; `fromScopeId` for `move` and `merge`; `sourceId` (the page merged away) for `merge` |
| `note`  | `add`, `restamp`, `remove`, `restore`         | `pageId`, `noteId`                                                                                       |
| `pin`   | `add`, `remove`                               | `pageId`                                                                                                 |

Every event also has `knowledgeId` and `at`. Creating a scope emits one `scope` event, not one per child scope or template page, so re-list the scope when it arrives. A listener that throws is logged and doesn't fail the write.

```typescript
const unsubscribe = knowledge.onChange(event => {
  if (event.kind === 'page') refreshPage(event.pageId)
})
```

### Properties

#### `pinnedContextEnabled`

`boolean`. Whether `pinnedContext` is on, so attached agents get pinned pages every turn.

## Related

- [`knowledgeMemoryScopes()`](https://mastra.ai/reference/knowledge/knowledge-memory-scopes)
- [Knowledge tools](https://mastra.ai/reference/knowledge/knowledge-tools)
- [Scope declarations](https://mastra.ai/reference/knowledge/scope-declarations)
- [Scopes and access](https://mastra.ai/docs/knowledge/scopes-and-access)