Defined in: [src/mcp/client.ts:319](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L319) MCP client using SDK v2, including legacy task execution. ## Example ```typescript const client = new McpClient({ url: 'https://example.com/mcp', tasksConfig: {} }) const agent = new Agent({ tools: [client] }) ``` ## Constructors ### Constructor ```ts new McpClient(args): McpClient; ``` Defined in: [src/mcp/client.ts:401](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L401) #### Parameters | Parameter | Type | | --- | --- | | `args` | [`McpClientConfig`](/docs/api/typescript/McpClientConfig/index.md) | #### Returns `McpClient` ## Properties ### ~DEFAULT\_TTL~ ```ts readonly static DEFAULT_TTL: 60000 = 60000; ``` Defined in: [src/mcp/client.ts:325](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L325) Default task lifecycle request timeout in milliseconds. #### Deprecated Use [McpClient.DEFAULT\_REQUEST\_TIMEOUT](#default_request_timeout). --- ### DEFAULT\_POLL\_TIMEOUT ```ts readonly static DEFAULT_POLL_TIMEOUT: 300000 = 300000; ``` Defined in: [src/mcp/client.ts:328](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L328) Default overall task operation deadline in milliseconds. --- ### DEFAULT\_REQUEST\_TIMEOUT ```ts readonly static DEFAULT_REQUEST_TIMEOUT: 60000 = 60000; ``` Defined in: [src/mcp/client.ts:331](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L331) Default task lifecycle request timeout in milliseconds. --- ### DEFAULT\_POLL\_INTERVAL\_MS ```ts readonly static DEFAULT_POLL_INTERVAL_MS: 1000 = 1000; ``` Defined in: [src/mcp/client.ts:334](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L334) Default polling interval when a legacy task response omits `pollInterval`. ## Accessors ### client #### Get Signature ```ts get client(): Client; ``` Defined in: [src/mcp/client.ts:511](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L511) ##### Returns `Client` --- ### serverCapabilities #### Get Signature ```ts get serverCapabilities(): any; ``` Defined in: [src/mcp/client.ts:515](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L515) ##### Returns `any` --- ### serverVersion #### Get Signature ```ts get serverVersion(): any; ``` Defined in: [src/mcp/client.ts:519](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L519) ##### Returns `any` --- ### serverInstructions #### Get Signature ```ts get serverInstructions(): string; ``` Defined in: [src/mcp/client.ts:523](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L523) ##### Returns `string` --- ### connectionState #### Get Signature ```ts get connectionState(): McpConnectionState; ``` Defined in: [src/mcp/client.ts:527](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L527) ##### Returns [`McpConnectionState`](/docs/api/typescript/McpConnectionState/index.md) --- ### clientName #### Get Signature ```ts get clientName(): string; ``` Defined in: [src/mcp/client.ts:531](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L531) ##### Returns `string` --- ### continueOnError #### Get Signature ```ts get continueOnError(): boolean; ``` Defined in: [src/mcp/client.ts:535](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L535) ##### Returns `boolean` --- ### onToolsChanged #### Set Signature ```ts set onToolsChanged(callback): void; ``` Defined in: [src/mcp/client.ts:751](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L751) Sets a callback invoked when the MCP server’s tool list changes at runtime. ##### Parameters | Parameter | Type | Description | | --- | --- | --- | | `callback` | (`oldTools`, `newTools`) => `void` | Handler receiving the previous tool names and the refreshed tool instances, or undefined to remove the callback. | ##### Returns `void` ## Methods ### loadServers() ```ts static loadServers( config, defaults?, options? ): Promise; ``` Defined in: [src/mcp/client.ts:344](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L344) Parses an MCP servers config (file path or object) and returns McpClient instances. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `config` | | `string` | `Record`<`string`, [`McpServerConfig`](/docs/api/typescript/McpServerConfig/index.md)\> | A file path to a JSON config, or a flat server map object. | | `defaults?` | [`McpClientOptions`](/docs/api/typescript/McpClientOptions/index.md) | Options applied to all clients unless overridden per-server. | | `options?` | [`McpLoadServersOptions`](/docs/api/typescript/McpLoadServersOptions/index.md) | Loader behavior, such as prefixing tools with the server name. | #### Returns `Promise`<`McpClient`\[\]> An array of McpClient instances ready to be passed to an Agent. --- ### connect() ```ts connect(reconnect?, options?): Promise; ``` Defined in: [src/mcp/client.ts:569](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L569) Connects the MCP client to the server. Called lazily before any operation that requires a connection. When `continueOnError` is true, connection failures are swallowed and the client enters a `'failed'` state. Subsequent calls are then no-ops until `connect(true)` is called explicitly to retry. A client configured with `url` retries on a fresh transport and connection. A client configured with a `transport` instance reuses it, so the retry only works when that transport can be started again (a `StreamableHTTPClientTransport` cannot, so construct a new `McpClient` instead). #### Parameters | Parameter | Type | Default value | Description | | --- | --- | --- | --- | | `reconnect` | `boolean` | `false` | When true, forces a reconnect even if already connected or failed. | | `options?` | { `signal?`: `AbortSignal`; } | `undefined` | Optional abort signal that stops this caller’s wait. The connection attempt itself continues for other callers awaiting it. | | `options.signal?` | `AbortSignal` | `undefined` | \- | #### Returns `Promise`<`void`\> A promise that resolves when the connection is established. --- ### disconnect() ```ts disconnect(): Promise; ``` Defined in: [src/mcp/client.ts:650](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L650) Disconnects the MCP client from the server and cleans up resources. #### Returns `Promise`<`void`\> A promise that resolves when the disconnection is complete. --- ### \[asyncDispose\]() ```ts asyncDispose: Promise; ``` Defined in: [src/mcp/client.ts:667](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L667) Enables the `await using` pattern for automatic resource cleanup. Delegates to [McpClient.disconnect](#disconnect). #### Returns `Promise`<`void`\> --- ### listTools() ```ts listTools(options?): Promise; ``` Defined in: [src/mcp/client.ts:683](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L683) Lists the tools available on the server and returns them as executable McpTool instances. A prefix renames tools for the agent only; tools are always invoked, and matched by string and `RegExp` filters, under their server-side name. Overlong prefixed names are skipped with a warning when `continueOnError` is true; otherwise, listing throws. Unprefixed names are not length-checked. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `options?` | [`McpListToolsOptions`](/docs/api/typescript/McpListToolsOptions/index.md) | Overrides for the prefix and filters set on the client. An omitted field uses the client’s value; an explicit empty string or empty object disables it. | #### Returns `Promise`<`McpTool`\[\]> A promise that resolves with an array of McpTool instances. #### Throws ToolValidationError When a prefixed name exceeds the registry limit and `continueOnError` is false. --- ### listPrompts() ```ts listPrompts(options?): Promise; ``` Defined in: [src/mcp/client.ts:789](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L789) Lists the prompts available on the server. Without a `paginationToken` the client aggregates every page into one result with no `nextCursor`, and throws `ListPaginationExceeded` when the server pages past `listMaxPages` (64 unless configured). With a token it fetches a single page whose `nextCursor` feeds the next call. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `options?` | [`McpListOptions`](/docs/api/typescript/McpListOptions/index.md) | Pagination options. | #### Returns `Promise`<`ListPromptsResult`\> A promise that resolves with the raw MCP list prompts result. #### Throws Error when an earlier connect attempt failed with `continueOnError` set. Call `connect(true)` to retry. --- ### getPrompt() ```ts getPrompt(promptId, args?): Promise; ``` Defined in: [src/mcp/client.ts:802](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L802) Retrieves a prompt from the server by name. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `promptId` | `string` | The name of the prompt to retrieve. | | `args?` | `Record`<`string`, `string`\> | Arguments for the prompt’s template substitution. | #### Returns `Promise`<`GetPromptResult`\> A promise that resolves with the raw MCP prompt result. #### Throws Error when an earlier connect attempt failed with `continueOnError` set. Call `connect(true)` to retry. --- ### listResources() ```ts listResources(options?): Promise; ``` Defined in: [src/mcp/client.ts:819](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L819) Lists the resources available on the server. Without a `paginationToken` the client aggregates every page into one result with no `nextCursor`, and throws `ListPaginationExceeded` when the server pages past `listMaxPages` (64 unless configured). With a token it fetches a single page whose `nextCursor` feeds the next call. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `options?` | [`McpListOptions`](/docs/api/typescript/McpListOptions/index.md) | Pagination options. | #### Returns `Promise`<`ListResourcesResult`\> A promise that resolves with the raw MCP list resources result. #### Throws Error when an earlier connect attempt failed with `continueOnError` set. Call `connect(true)` to retry. --- ### readResource() ```ts readResource(uri): Promise; ``` Defined in: [src/mcp/client.ts:831](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L831) Reads a resource from the server. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `uri` | `string` | `URL` | The URI of the resource to read. | #### Returns `Promise`<`ReadResourceResult`\> A promise that resolves with the raw MCP resource content. #### Throws Error when an earlier connect attempt failed with `continueOnError` set. Call `connect(true)` to retry. --- ### listResourceTemplates() ```ts listResourceTemplates(options?): Promise; ``` Defined in: [src/mcp/client.ts:848](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L848) Lists the resource templates available on the server. Without a `paginationToken` the client aggregates every page into one result with no `nextCursor`, and throws `ListPaginationExceeded` when the server pages past `listMaxPages` (64 unless configured). With a token it fetches a single page whose `nextCursor` feeds the next call. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `options?` | [`McpListOptions`](/docs/api/typescript/McpListOptions/index.md) | Pagination options. | #### Returns `Promise`<`ListResourceTemplatesResult`\> A promise that resolves with the raw MCP list resource templates result. #### Throws Error when an earlier connect attempt failed with `continueOnError` set. Call `connect(true)` to retry. --- ### callTool() ```ts callTool( tool, args, options? ): Promise; ``` Defined in: [src/mcp/client.ts:867](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L867) Invoke a tool on the connected MCP server using an McpTool instance. When `tasksConfig` is set, task-backed execution is completed automatically on both server generations: SEP-2663 tasks on servers that advertise the tasks extension, and the legacy 2025-11-25 task protocol. Direct tool results are returned unchanged. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `tool` | `McpTool` | The McpTool instance to invoke. | | `args` | [`JSONValue`](/docs/api/typescript/JSONValue/index.md) | The arguments to pass to the tool. | | `options?` | [`McpCallToolOptions`](/docs/api/typescript/McpCallToolOptions/index.md) | Optional settings for the request. | #### Returns `Promise`<[`JSONValue`](/docs/api/typescript/JSONValue/index.md)\> The final tool result. #### Throws [McpTaskCancelledError](/docs/api/typescript/McpTaskCancelledError/index.md) When the server reports a cancelled task. #### Throws [McpTaskFailedError](/docs/api/typescript/McpTaskFailedError/index.md) When the server reports a failed task. --- ### submitTool() ```ts submitTool( tool, args, options? ): Promise; ``` Defined in: [src/mcp/client.ts:910](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L910) Invokes a tool once and returns either its direct result or a server-created task handle. This operation never polls or consumes a returned task handle. Task creation is controlled by the server; the client only advertises support when `tasksConfig` is configured. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `tool` | `McpTool` | The McpTool instance to invoke. | | `args` | [`JSONValue`](/docs/api/typescript/JSONValue/index.md) | The arguments to pass to the tool. | | `options?` | [`McpCallToolOptions`](/docs/api/typescript/McpCallToolOptions/index.md) | Optional settings for the request. | #### Returns `Promise`<`any`\> The direct tool result or task handle returned by the server. --- ### getTask() ```ts getTask(taskId, options?): Promise; ``` Defined in: [src/mcp/client.ts:959](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L959) Retrieves the current state of a SEP-2663 task. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `taskId` | `string` | Server-issued task identifier. | | `options?` | [`McpTaskRequestOptions`](/docs/api/typescript/McpTaskRequestOptions/index.md) | Optional lifecycle request settings. | #### Returns `Promise`<[`McpGetTaskResult`](/docs/api/typescript/McpGetTaskResult/index.md)\> The validated task state, including terminal result or error data when present. --- ### updateTask() ```ts updateTask( taskId, inputResponses, options? ): Promise; ``` Defined in: [src/mcp/client.ts:980](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L980) Supplies one or more responses to outstanding task input requests. Partial response sets are supported; the server may keep the task in `input_required` until every outstanding request has been answered. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `taskId` | `string` | Server-issued task identifier. | | `inputResponses` | [`McpInputResponses`](/docs/api/typescript/McpInputResponses/index.md) | Responses keyed by the corresponding input request key. | | `options?` | [`McpTaskRequestOptions`](/docs/api/typescript/McpTaskRequestOptions/index.md) | Optional lifecycle request settings. | #### Returns `Promise`<[`McpUpdateTaskResult`](/docs/api/typescript/McpUpdateTaskResult/index.md)\> The server’s validated acknowledgement. --- ### cancelTask() ```ts cancelTask(taskId, options?): Promise; ``` Defined in: [src/mcp/client.ts:1009](https://github.com/strands-agents/harness-sdk/blob/main/strands-ts/src/mcp/client.ts#L1009) Requests cooperative cancellation of a SEP-2663 task. A successful acknowledgement does not guarantee that the server stopped the work or that the task will eventually report `cancelled`. #### Parameters | Parameter | Type | Description | | --- | --- | --- | | `taskId` | `string` | Server-issued task identifier. | | `options?` | [`McpTaskRequestOptions`](/docs/api/typescript/McpTaskRequestOptions/index.md) | Optional lifecycle request settings. | #### Returns `Promise`<[`McpCancelTaskResult`](/docs/api/typescript/McpCancelTaskResult/index.md)\> The server’s validated acknowledgement.