xmcp/dist/types/mcp-middleware.d.ts

The TypeScript MCP framework

import type { HandlerResultTypeMap, Icon, RequestTypeMap } from "@modelcontextprotocol/server";
import type { RequestContext } from "../runtime/contexts/request-context";
import type { ToolAnnotations } from "./tool";
export type McpMiddlewareMethod = "tools/call" | "tools/list" | "prompts/get" | "prompts/list" | "resources/read" | "resources/list" | "resources/templates/list" | "completion/complete";
/** Registered tool metadata; _meta uses the same normalized keys as tools/list. */
export interface McpToolMetadata {
    readonly name: string;
    readonly description: string;
    readonly annotations?: Readonly<ToolAnnotations>;
    readonly icons?: readonly Readonly<Icon>[];
    readonly tags?: readonly string[];
    readonly _meta?: Readonly<Record<string, unknown>>;
}
/** Narrow by method before accessing operation-specific parameters. */
export type McpMiddlewareContext = {
    [M in McpMiddlewareMethod]: RequestContext & {
        readonly method: M;
        readonly params: M extends "tools/call" ? {
            readonly name: string;
            readonly arguments: Readonly<Record<string, unknown>>;
        } : Readonly<NonNullable<RequestTypeMap[M]["params"]>>;
    } & (M extends "tools/call" ? {
        readonly tool: {
            readonly metadata: McpToolMetadata;
        };
    } : {});
}[McpMiddlewareMethod];
export type McpMiddlewareResult = HandlerResultTypeMap[McpMiddlewareMethod];
export type McpMiddlewareNext = () => Promise<McpMiddlewareResult>;
/** Return a result directly to short-circuit, or await next() once. */
export type McpMiddleware = (ctx: McpMiddlewareContext, next: McpMiddlewareNext) => McpMiddlewareResult | Promise<McpMiddlewareResult>;