> ## Documentation Index
> Fetch the complete documentation index at: https://fastmcp-ts.docs.prefect.io/llms.txt
> Use this file to discover all available pages before exploring further.

# ClientSecretCredentialsOptions

Defined in: [client/auth.ts:530](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L530)

Shared-secret configuration for [ClientCredentials](/api/client/classes/ClientCredentials).

`authMethod` selects how the secret reaches the token endpoint:

* `client_secret_post` (default) — `client_id` and `client_secret` in the
  POST body. Unchanged from earlier releases.
* `client_secret_basic` — an RFC 6749 §2.3.1 HTTP Basic `Authorization`
  header. Nothing secret goes in the body.

## Extends

* `ClientCredentialsBaseOptions`

## Properties

### algorithm?

```ts theme={null}
optional algorithm?: undefined;
```

Defined in: [client/auth.ts:535](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L535)

***

### authMethod?

```ts theme={null}
optional authMethod?: ClientSecretAuthMethod;
```

Defined in: [client/auth.ts:533](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L533)

Token-endpoint authentication method. Default: `client_secret_post`.

***

### clientId

```ts theme={null}
clientId: string;
```

Defined in: [client/auth.ts:506](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L506)

#### Inherited from

```ts theme={null}
ClientCredentialsBaseOptions.clientId
```

***

### clientSecret

```ts theme={null}
clientSecret: string;
```

Defined in: [client/auth.ts:531](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L531)

***

### privateKey?

```ts theme={null}
optional privateKey?: undefined;
```

Defined in: [client/auth.ts:534](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L534)

***

### refreshBufferSeconds?

```ts theme={null}
optional refreshBufferSeconds?: number;
```

Defined in: [client/auth.ts:518](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L518)

How many seconds before expiry to proactively re-fetch. Default: 60.

#### Inherited from

```ts theme={null}
ClientCredentialsBaseOptions.refreshBufferSeconds
```

***

### scope?

```ts theme={null}
optional scope?: string;
```

Defined in: [client/auth.ts:507](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L507)

#### Inherited from

```ts theme={null}
ClientCredentialsBaseOptions.scope
```

***

### store?

```ts theme={null}
optional store?: KeyValueStore;
```

Defined in: [client/auth.ts:516](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L516)

Persistent token store. Default: in-memory. The cache key is derived from
`tokenEndpoint` alone, with no client identity in it — use one store per
credential identity. Do not share a persistent `store` across two
`ClientCredentials` instances that have different `clientId`/`clientSecret`/
`privateKey` but the same `tokenEndpoint`; they will read and overwrite
each other's cached tokens.

#### Inherited from

```ts theme={null}
ClientCredentialsBaseOptions.store
```

***

### tokenEndpoint

```ts theme={null}
tokenEndpoint: string;
```

Defined in: [client/auth.ts:505](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/auth.ts#L505)

#### Inherited from

```ts theme={null}
ClientCredentialsBaseOptions.tokenEndpoint
```