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type CacheKeyFn = (ctx) => string;
Defined in: server/middleware.ts:123 Custom cache key function. Receives the full middleware context so callers can incorporate auth identity or any other dimension into the key. Required when using per-component auth checks. The default key is "method:JSON(params)", which contains no auth information. If auth-filtered list results (tools, resources, prompts) are cached with the default key, one session’s filtered results can be served to a session with different permissions. Pass a keyFn that includes the caller identity, e.g.: 
new CachingMiddleware(60_000, (ctx) =>
  `${ctx.method}:${ctx.mcpContext.auth?.clientId ?? ''}:${JSON.stringify(ctx.request)}`
)

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Parameters

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ctx

MiddlewareContext

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Returns

string