Codebase MCP
- src
- server
import {
mergeCapabilities,
Protocol,
ProtocolOptions,
RequestOptions,
} from "../shared/protocol.js";
import {
ClientCapabilities,
CreateMessageRequest,
CreateMessageResultSchema,
EmptyResultSchema,
Implementation,
InitializedNotificationSchema,
InitializeRequest,
InitializeRequestSchema,
InitializeResult,
LATEST_PROTOCOL_VERSION,
ListRootsRequest,
ListRootsResultSchema,
LoggingMessageNotification,
Notification,
Request,
ResourceUpdatedNotification,
Result,
ServerCapabilities,
ServerNotification,
ServerRequest,
ServerResult,
SUPPORTED_PROTOCOL_VERSIONS,
} from "../types.js";
export type ServerOptions = ProtocolOptions & {
/**
* Capabilities to advertise as being supported by this server.
*/
capabilities?: ServerCapabilities;
/**
* Optional instructions describing how to use the server and its features.
*/
instructions?: string;
};
/**
* An MCP server on top of a pluggable transport.
*
* This server will automatically respond to the initialization flow as initiated from the client.
*
* To use with custom types, extend the base Request/Notification/Result types and pass them as type parameters:
*
* ```typescript
* // Custom schemas
* const CustomRequestSchema = RequestSchema.extend({...})
* const CustomNotificationSchema = NotificationSchema.extend({...})
* const CustomResultSchema = ResultSchema.extend({...})
*
* // Type aliases
* type CustomRequest = z.infer<typeof CustomRequestSchema>
* type CustomNotification = z.infer<typeof CustomNotificationSchema>
* type CustomResult = z.infer<typeof CustomResultSchema>
*
* // Create typed server
* const server = new Server<CustomRequest, CustomNotification, CustomResult>({
* name: "CustomServer",
* version: "1.0.0"
* })
* ```
*/
export class Server<
RequestT extends Request = Request,
NotificationT extends Notification = Notification,
ResultT extends Result = Result,
> extends Protocol<
ServerRequest | RequestT,
ServerNotification | NotificationT,
ServerResult | ResultT
> {
private _clientCapabilities?: ClientCapabilities;
private _clientVersion?: Implementation;
private _capabilities: ServerCapabilities;
private _instructions?: string;
/**
* Callback for when initialization has fully completed (i.e., the client has sent an `initialized` notification).
*/
oninitialized?: () => void;
/**
* Initializes this server with the given name and version information.
*/
constructor(
private _serverInfo: Implementation,
options?: ServerOptions,
) {
super(options);
this._capabilities = options?.capabilities ?? {};
this._instructions = options?.instructions;
this.setRequestHandler(InitializeRequestSchema, (request) =>
this._oninitialize(request),
);
this.setNotificationHandler(InitializedNotificationSchema, () =>
this.oninitialized?.(),
);
}
/**
* Registers new capabilities. This can only be called before connecting to a transport.
*
* The new capabilities will be merged with any existing capabilities previously given (e.g., at initialization).
*/
public registerCapabilities(capabilities: ServerCapabilities): void {
if (this.transport) {
throw new Error(
"Cannot register capabilities after connecting to transport",
);
}
this._capabilities = mergeCapabilities(this._capabilities, capabilities);
}
protected assertCapabilityForMethod(method: RequestT["method"]): void {
switch (method as ServerRequest["method"]) {
case "sampling/createMessage":
if (!this._clientCapabilities?.sampling) {
throw new Error(
`Client does not support sampling (required for ${method})`,
);
}
break;
case "roots/list":
if (!this._clientCapabilities?.roots) {
throw new Error(
`Client does not support listing roots (required for ${method})`,
);
}
break;
case "ping":
// No specific capability required for ping
break;
}
}
protected assertNotificationCapability(
method: (ServerNotification | NotificationT)["method"],
): void {
switch (method as ServerNotification["method"]) {
case "notifications/message":
if (!this._capabilities.logging) {
throw new Error(
`Server does not support logging (required for ${method})`,
);
}
break;
case "notifications/resources/updated":
case "notifications/resources/list_changed":
if (!this._capabilities.resources) {
throw new Error(
`Server does not support notifying about resources (required for ${method})`,
);
}
break;
case "notifications/tools/list_changed":
if (!this._capabilities.tools) {
throw new Error(
`Server does not support notifying of tool list changes (required for ${method})`,
);
}
break;
case "notifications/prompts/list_changed":
if (!this._capabilities.prompts) {
throw new Error(
`Server does not support notifying of prompt list changes (required for ${method})`,
);
}
break;
case "notifications/cancelled":
// Cancellation notifications are always allowed
break;
case "notifications/progress":
// Progress notifications are always allowed
break;
}
}
protected assertRequestHandlerCapability(method: string): void {
switch (method) {
case "sampling/createMessage":
if (!this._capabilities.sampling) {
throw new Error(
`Server does not support sampling (required for ${method})`,
);
}
break;
case "logging/setLevel":
if (!this._capabilities.logging) {
throw new Error(
`Server does not support logging (required for ${method})`,
);
}
break;
case "prompts/get":
case "prompts/list":
if (!this._capabilities.prompts) {
throw new Error(
`Server does not support prompts (required for ${method})`,
);
}
break;
case "resources/list":
case "resources/templates/list":
case "resources/read":
if (!this._capabilities.resources) {
throw new Error(
`Server does not support resources (required for ${method})`,
);
}
break;
case "tools/call":
case "tools/list":
if (!this._capabilities.tools) {
throw new Error(
`Server does not support tools (required for ${method})`,
);
}
break;
case "ping":
case "initialize":
// No specific capability required for these methods
break;
}
}
private async _oninitialize(
request: InitializeRequest,
): Promise<InitializeResult> {
const requestedVersion = request.params.protocolVersion;
this._clientCapabilities = request.params.capabilities;
this._clientVersion = request.params.clientInfo;
return {
protocolVersion: SUPPORTED_PROTOCOL_VERSIONS.includes(requestedVersion)
? requestedVersion
: LATEST_PROTOCOL_VERSION,
capabilities: this.getCapabilities(),
serverInfo: this._serverInfo,
...(this._instructions && { instructions: this._instructions }),
};
}
/**
* After initialization has completed, this will be populated with the client's reported capabilities.
*/
getClientCapabilities(): ClientCapabilities | undefined {
return this._clientCapabilities;
}
/**
* After initialization has completed, this will be populated with information about the client's name and version.
*/
getClientVersion(): Implementation | undefined {
return this._clientVersion;
}
private getCapabilities(): ServerCapabilities {
return this._capabilities;
}
async ping() {
return this.request({ method: "ping" }, EmptyResultSchema);
}
async createMessage(
params: CreateMessageRequest["params"],
options?: RequestOptions,
) {
return this.request(
{ method: "sampling/createMessage", params },
CreateMessageResultSchema,
options,
);
}
async listRoots(
params?: ListRootsRequest["params"],
options?: RequestOptions,
) {
return this.request(
{ method: "roots/list", params },
ListRootsResultSchema,
options,
);
}
async sendLoggingMessage(params: LoggingMessageNotification["params"]) {
return this.notification({ method: "notifications/message", params });
}
async sendResourceUpdated(params: ResourceUpdatedNotification["params"]) {
return this.notification({
method: "notifications/resources/updated",
params,
});
}
async sendResourceListChanged() {
return this.notification({
method: "notifications/resources/list_changed",
});
}
async sendToolListChanged() {
return this.notification({ method: "notifications/tools/list_changed" });
}
async sendPromptListChanged() {
return this.notification({ method: "notifications/prompts/list_changed" });
}
}