server.js 9.9 KB

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  1. /**
  2. * Experimental server task features for MCP SDK.
  3. * WARNING: These APIs are experimental and may change without notice.
  4. *
  5. * @experimental
  6. */
  7. import { CreateMessageResultSchema, ElicitResultSchema } from '../../types.js';
  8. /**
  9. * Experimental task features for low-level MCP servers.
  10. *
  11. * Access via `server.experimental.tasks`:
  12. * ```typescript
  13. * const stream = server.experimental.tasks.requestStream(request, schema, options);
  14. * ```
  15. *
  16. * For high-level server usage with task-based tools, use `McpServer.experimental.tasks` instead.
  17. *
  18. * @experimental
  19. */
  20. export class ExperimentalServerTasks {
  21. constructor(_server) {
  22. this._server = _server;
  23. }
  24. /**
  25. * Sends a request and returns an AsyncGenerator that yields response messages.
  26. * The generator is guaranteed to end with either a 'result' or 'error' message.
  27. *
  28. * This method provides streaming access to request processing, allowing you to
  29. * observe intermediate task status updates for task-augmented requests.
  30. *
  31. * @param request - The request to send
  32. * @param resultSchema - Zod schema for validating the result
  33. * @param options - Optional request options (timeout, signal, task creation params, etc.)
  34. * @returns AsyncGenerator that yields ResponseMessage objects
  35. *
  36. * @experimental
  37. */
  38. requestStream(request, resultSchema, options) {
  39. return this._server.requestStream(request, resultSchema, options);
  40. }
  41. /**
  42. * Sends a sampling request and returns an AsyncGenerator that yields response messages.
  43. * The generator is guaranteed to end with either a 'result' or 'error' message.
  44. *
  45. * For task-augmented requests, yields 'taskCreated' and 'taskStatus' messages
  46. * before the final result.
  47. *
  48. * @example
  49. * ```typescript
  50. * const stream = server.experimental.tasks.createMessageStream({
  51. * messages: [{ role: 'user', content: { type: 'text', text: 'Hello' } }],
  52. * maxTokens: 100
  53. * }, {
  54. * onprogress: (progress) => {
  55. * // Handle streaming tokens via progress notifications
  56. * console.log('Progress:', progress.message);
  57. * }
  58. * });
  59. *
  60. * for await (const message of stream) {
  61. * switch (message.type) {
  62. * case 'taskCreated':
  63. * console.log('Task created:', message.task.taskId);
  64. * break;
  65. * case 'taskStatus':
  66. * console.log('Task status:', message.task.status);
  67. * break;
  68. * case 'result':
  69. * console.log('Final result:', message.result);
  70. * break;
  71. * case 'error':
  72. * console.error('Error:', message.error);
  73. * break;
  74. * }
  75. * }
  76. * ```
  77. *
  78. * @param params - The sampling request parameters
  79. * @param options - Optional request options (timeout, signal, task creation params, onprogress, etc.)
  80. * @returns AsyncGenerator that yields ResponseMessage objects
  81. *
  82. * @experimental
  83. */
  84. createMessageStream(params, options) {
  85. // Access client capabilities via the server
  86. const clientCapabilities = this._server.getClientCapabilities();
  87. // Capability check - only required when tools/toolChoice are provided
  88. if ((params.tools || params.toolChoice) && !clientCapabilities?.sampling?.tools) {
  89. throw new Error('Client does not support sampling tools capability.');
  90. }
  91. // Message structure validation - always validate tool_use/tool_result pairs.
  92. // These may appear even without tools/toolChoice in the current request when
  93. // a previous sampling request returned tool_use and this is a follow-up with results.
  94. if (params.messages.length > 0) {
  95. const lastMessage = params.messages[params.messages.length - 1];
  96. const lastContent = Array.isArray(lastMessage.content) ? lastMessage.content : [lastMessage.content];
  97. const hasToolResults = lastContent.some(c => c.type === 'tool_result');
  98. const previousMessage = params.messages.length > 1 ? params.messages[params.messages.length - 2] : undefined;
  99. const previousContent = previousMessage
  100. ? Array.isArray(previousMessage.content)
  101. ? previousMessage.content
  102. : [previousMessage.content]
  103. : [];
  104. const hasPreviousToolUse = previousContent.some(c => c.type === 'tool_use');
  105. if (hasToolResults) {
  106. if (lastContent.some(c => c.type !== 'tool_result')) {
  107. throw new Error('The last message must contain only tool_result content if any is present');
  108. }
  109. if (!hasPreviousToolUse) {
  110. throw new Error('tool_result blocks are not matching any tool_use from the previous message');
  111. }
  112. }
  113. if (hasPreviousToolUse) {
  114. // Extract tool_use IDs from previous message and tool_result IDs from current message
  115. const toolUseIds = new Set(previousContent.filter(c => c.type === 'tool_use').map(c => c.id));
  116. const toolResultIds = new Set(lastContent.filter(c => c.type === 'tool_result').map(c => c.toolUseId));
  117. if (toolUseIds.size !== toolResultIds.size || ![...toolUseIds].every(id => toolResultIds.has(id))) {
  118. throw new Error('ids of tool_result blocks and tool_use blocks from previous message do not match');
  119. }
  120. }
  121. }
  122. return this.requestStream({
  123. method: 'sampling/createMessage',
  124. params
  125. }, CreateMessageResultSchema, options);
  126. }
  127. /**
  128. * Sends an elicitation request and returns an AsyncGenerator that yields response messages.
  129. * The generator is guaranteed to end with either a 'result' or 'error' message.
  130. *
  131. * For task-augmented requests (especially URL-based elicitation), yields 'taskCreated'
  132. * and 'taskStatus' messages before the final result.
  133. *
  134. * @example
  135. * ```typescript
  136. * const stream = server.experimental.tasks.elicitInputStream({
  137. * mode: 'url',
  138. * message: 'Please authenticate',
  139. * elicitationId: 'auth-123',
  140. * url: 'https://example.com/auth'
  141. * }, {
  142. * task: { ttl: 300000 } // Task-augmented for long-running auth flow
  143. * });
  144. *
  145. * for await (const message of stream) {
  146. * switch (message.type) {
  147. * case 'taskCreated':
  148. * console.log('Task created:', message.task.taskId);
  149. * break;
  150. * case 'taskStatus':
  151. * console.log('Task status:', message.task.status);
  152. * break;
  153. * case 'result':
  154. * console.log('User action:', message.result.action);
  155. * break;
  156. * case 'error':
  157. * console.error('Error:', message.error);
  158. * break;
  159. * }
  160. * }
  161. * ```
  162. *
  163. * @param params - The elicitation request parameters
  164. * @param options - Optional request options (timeout, signal, task creation params, etc.)
  165. * @returns AsyncGenerator that yields ResponseMessage objects
  166. *
  167. * @experimental
  168. */
  169. elicitInputStream(params, options) {
  170. // Access client capabilities via the server
  171. const clientCapabilities = this._server.getClientCapabilities();
  172. const mode = params.mode ?? 'form';
  173. // Capability check based on mode
  174. switch (mode) {
  175. case 'url': {
  176. if (!clientCapabilities?.elicitation?.url) {
  177. throw new Error('Client does not support url elicitation.');
  178. }
  179. break;
  180. }
  181. case 'form': {
  182. if (!clientCapabilities?.elicitation?.form) {
  183. throw new Error('Client does not support form elicitation.');
  184. }
  185. break;
  186. }
  187. }
  188. // Normalize params to ensure mode is set for form mode (defaults to 'form' per spec)
  189. const normalizedParams = mode === 'form' && params.mode === undefined ? { ...params, mode: 'form' } : params;
  190. // Cast to ServerRequest needed because TypeScript can't narrow the union type
  191. // based on the discriminated 'method' field when constructing the object literal
  192. return this.requestStream({
  193. method: 'elicitation/create',
  194. params: normalizedParams
  195. }, ElicitResultSchema, options);
  196. }
  197. /**
  198. * Gets the current status of a task.
  199. *
  200. * @param taskId - The task identifier
  201. * @param options - Optional request options
  202. * @returns The task status
  203. *
  204. * @experimental
  205. */
  206. async getTask(taskId, options) {
  207. return this._server.getTask({ taskId }, options);
  208. }
  209. /**
  210. * Retrieves the result of a completed task.
  211. *
  212. * @param taskId - The task identifier
  213. * @param resultSchema - Zod schema for validating the result
  214. * @param options - Optional request options
  215. * @returns The task result
  216. *
  217. * @experimental
  218. */
  219. async getTaskResult(taskId, resultSchema, options) {
  220. return this._server.getTaskResult({ taskId }, resultSchema, options);
  221. }
  222. /**
  223. * Lists tasks with optional pagination.
  224. *
  225. * @param cursor - Optional pagination cursor
  226. * @param options - Optional request options
  227. * @returns List of tasks with optional next cursor
  228. *
  229. * @experimental
  230. */
  231. async listTasks(cursor, options) {
  232. return this._server.listTasks(cursor ? { cursor } : undefined, options);
  233. }
  234. /**
  235. * Cancels a running task.
  236. *
  237. * @param taskId - The task identifier
  238. * @param options - Optional request options
  239. *
  240. * @experimental
  241. */
  242. async cancelTask(taskId, options) {
  243. return this._server.cancelTask({ taskId }, options);
  244. }
  245. }
  246. //# sourceMappingURL=server.js.map