Client - FastMCP TS

Implements

IClient

Constructors

Constructor

new Client(input, options?): Client;

Defined in: client/client.ts:208

Parameters

input

ClientTransportInput

options?

ClientOptions

Returns

Client

Methods

[asyncDispose]()

asyncDispose: Promise<void>;

Defined in: client/client.ts:359

Returns

Promise<void>

Implementation of

IClient.[asyncDispose]

callTool()

callTool<TData>(
   name, 
   args?, 
   options?): Promise<CallToolResult<TData>>;

Defined in: client/client.ts:434

Type Parameters

TData

TData = unknown

Parameters

name

string

args?

Record<string, unknown>

options?

CallToolOptions

Returns

Promise<CallToolResult<TData>>

Implementation of

IClient.callTool

callToolRaw()

callToolRaw<TData>(
   name, 
   args?, 
   options?): Promise<CallToolResult<TData>>;

Defined in: client/client.ts:452 Returns the full result including isError without throwing.

Type Parameters

TData

TData = unknown

Parameters

name

string

args?

Record<string, unknown>

options?

CallToolOptions

Returns

Promise<CallToolResult<TData>>

close()

close(): Promise<void>;

Defined in: client/client.ts:342

Returns

Promise<void>

Implementation of

IClient.close

complete()

complete(
   ref, 
   argument, 
   context?, 
   options?): Promise<CompletionResult>;

Defined in: client/client.ts:629

Parameters

ref

| { name: string; type: "ref/prompt"; } | { type: "ref/resource"; uri: string; }

argument

name

string

value

string

context?

arguments?

Record<string, string>

connect()

connect(): Promise<void>;

Defined in: client/client.ts:236

Returns

Promise<void>

Implementation of

IClient.connect

getPrompt()

getPrompt(
   name, 
   args?, 
   options?): Promise<{
[key: string]: unknown;
}>;

Defined in: client/client.ts:611

Parameters

name

string

args?

Record<string, string>

options?

RequestOptions

Returns

Promise<{ [key: string]: unknown; }>

Implementation of

IClient.getPrompt

getProtocolEra()

getProtocolEra(): ProtocolEra | undefined;

Defined in: client/client.ts:416 The protocol era negotiated at connect(): 'modern' for 2026-07-28 (per-request envelope), 'legacy' for 2025-11-25 and earlier (the initialize handshake). undefined before connect(). See ClientOptions.versionNegotiation.

Returns

ProtocolEra | undefined

isConnected()

isConnected(): boolean;

Defined in: client/client.ts:363

Returns

boolean

Implementation of

IClient.isConnected

listPrompts()

listPrompts(options?): Promise<{
}[]>;

Defined in: client/client.ts:601

Parameters

options?

RequestOptions

Returns

Promise<{ }[]>

Implementation of

IClient.listPrompts

listResources()

listResources(options?): Promise<{
}[]>;

Defined in: client/client.ts:476

Parameters

options?

RequestOptions

Returns

Promise<{ }[]>

Implementation of

IClient.listResources

listResourceTemplates()

listResourceTemplates(options?): Promise<{
}[]>;

Defined in: client/client.ts:486

Parameters

options?

RequestOptions

Returns

Promise<{ }[]>

Implementation of

IClient.listResourceTemplates

listTools()

listTools(options?): Promise<{
}[]>;

Defined in: client/client.ts:424

Parameters

options?

RequestOptions

Returns

Promise<{ }[]>

Implementation of

IClient.listTools

notifyRootsChanged()

notifyRootsChanged(): Promise<void>;

Defined in: client/client.ts:908 Notify the connected server that the client’s roots list has changed. The server should re-issue a roots/list request to get the updated list.

Returns

Promise<void>

ping()

ping(options?): Promise<boolean>;

Defined in: client/client.ts:402 Liveness check. On a legacy-era connection this sends the ping RPC. On a modern (2026-07-28) connection ping is not a wire method — the era’s registry deliberately excludes it — so this sends server/discover instead: any successful response is equally strong liveness evidence, and discover() is the SDK-native modern equivalent (rather than a hand-rolled substitute). Returns false only on legacy ping’s own result; a modern-era failure throws, matching ping()’s existing throw-on-failure contract.

Parameters

options?

RequestOptions

Returns

Promise<boolean>

Implementation of

IClient.ping

readResource()

readResource(uri, options?): Promise<(
  | {
}
  | {
})[]>;

Defined in: client/client.ts:496

Parameters

uri

string

options?

RequestOptions

Returns

Promise<( | { } | { })[]>

Implementation of

IClient.readResource

readResourceRaw()

readResourceRaw(uri, options?): Promise<{
[key: string]: unknown;
}>;

Defined in: client/client.ts:510 Returns the raw SDK ReadResourceResult without unwrapping.

Parameters

uri

string

options?

RequestOptions

Returns

Promise<{ [key: string]: unknown; }>

setLogLevel()

setLogLevel(level, options?): Promise<void>;

Defined in: client/client.ts:658 Sets the minimum severity level for log messages sent by the server. On a legacy-era connection this sends the logging/setLevel RPC, unchanged. On a modern (2026-07-28) connection logging/setLevel is deprecated (SEP-2577) and physically absent from the era’s registry — there is no RPC to send. Instead, the level is recorded and threaded into _meta['io.modelcontextprotocol/logLevel'] on every subsequent request via _metaParams(), per request; user-supplied _meta still wins if a caller passes one explicitly (there is no such call site in this class today).

Parameters

level

LoggingLevel

options?

RequestOptions

Returns

Promise<void>

Implementation of

IClient.setLogLevel

subscribeResource()

subscribeResource(
   uri, 
   handler, 
   options?): Promise<void>;

Defined in: client/client.ts:528 Subscribes to change notifications for a resource URI. handler fires whenever the server sends a matching update, on either protocol era: on a legacy (2025-era) connection via the resources/subscribe RPC and unsolicited notifications/resources/updated push, or on a modern (2026-07-28) connection via a subscriptions/listen stream opted into resourceSubscriptions — both dispatch to the same notifications/resources/updated handler registered in _registerHandlers, so this method is the only era-aware part.

Parameters

uri

string

handler

ResourceUpdateHandler

options?

RequestOptions

Returns

Promise<void>

Implementation of

IClient.subscribeResource

unsubscribeResource()

unsubscribeResource(uri, options?): Promise<void>;

Defined in: client/client.ts:546

Parameters

uri

string

options?

RequestOptions

Returns

Promise<void>

Implementation of

IClient.unsubscribeResource

connect()

Call Signature

static connect(input, options?): Promise<MultiServerClient>;

Defined in: client/client.ts:368 Creates a connected MultiServerClient when given a multi-entry McpConfig.

Parameters

input

McpConfig

options?

MultiServerOptions

Returns

Promise<MultiServerClient>

Call Signature

static connect(input, options?): Promise<Client>;

Defined in: client/client.ts:370 Creates a connected Client for a single-server transport. Use with await using for automatic cleanup.

Parameters

input

ClientTransportInput

options?

ClientOptions

Returns

Promise<Client>

​Implements

​Constructors

​Constructor

​Parameters

input

options?

​Returns

​Methods

​[asyncDispose]()

​Returns

​Implementation of

​callTool()

​Type Parameters

TData

​Parameters

name

args?

options?

​Returns

​Implementation of

​callToolRaw()

​Type Parameters

TData

​Parameters

name

args?

options?

​Returns

​close()

​Returns

​Implementation of

​complete()

​Parameters

ref

argument

name

value

context?

arguments?

options?

​Returns

​Implementation of

​connect()

​Returns

​Implementation of

​getPrompt()

​Parameters

name

args?

options?

​Returns

​Implementation of

​getProtocolEra()

​Returns

​isConnected()

​Returns

​Implementation of

​listPrompts()

​Parameters

options?

​Returns

​Implementation of

​listResources()

​Parameters

options?

​Returns

​Implementation of

​listResourceTemplates()

​Parameters

options?

​Returns

​Implementation of

​listTools()

​Parameters

options?

​Returns

​Implementation of

​notifyRootsChanged()

​Returns

​ping()

Implements

Constructors

Constructor

Parameters

Returns

Methods

[asyncDispose]()

Returns

Implementation of

callTool()

Type Parameters

Parameters

Returns

Implementation of

callToolRaw()

Type Parameters

Parameters

Returns

close()

Returns

Implementation of

complete()

Parameters

Returns

Implementation of

connect()

Returns

Implementation of

getPrompt()

Parameters

Returns

Implementation of

getProtocolEra()

Returns

isConnected()

Returns

Implementation of

listPrompts()

Parameters

Returns

Implementation of

listResources()

Parameters

Returns

Implementation of

listResourceTemplates()

Parameters

Returns

Implementation of

listTools()

Parameters

Returns

Implementation of

notifyRootsChanged()

Returns

ping()

Parameters

Returns

Implementation of

readResource()

Parameters

Returns

Implementation of

readResourceRaw()

Parameters

Returns

setLogLevel()

Parameters

Returns

Implementation of

subscribeResource()

Parameters

Returns

Implementation of

unsubscribeResource()

Parameters

Returns

Implementation of

connect()

Call Signature