modelcontextprotocol/ext-apps
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refactor: use MCP resource types for ui/download-file params

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Replace custom {filename, content, mimeType, encoding} params with
standard MCP resource types: EmbeddedResource for inline content and
ResourceLink for host-resolved references.

New params shape:
  params: { contents: (EmbeddedResource | ResourceLink)[] }

This reuses existing MCP primitives instead of inventing new ones,
and enables hosts to show resource 'bubbles' or resolve ResourceLink
URIs via resources/read on the MCP server.
This commit is contained in:
Anton Pidkuiko MacBook 2026-02-20 12:00:35 +00:00
commit 3757271641
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1 changed files with 366 additions and 125 deletions
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44
src/app.ts
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@ -939,32 +939,56 @@ export class App extends Protocol<AppRequest, AppNotification, AppResult> {
* this provides a host-mediated mechanism for file exports. The host will
* typically show a confirmation dialog before initiating the download.
*
* @param params - File content, filename, MIME type, and optional encoding
* Uses standard MCP resource types: `EmbeddedResource` for inline content
* and `ResourceLink` for content the host can fetch directly.
*
* @param params - Resource contents to download
* @param options - Request options (timeout, etc.)
* @returns Result with `isError: true` if the host denied the request (e.g., user cancelled)
*
* @throws {Error} If the request times out or the connection is lost
*
* @example Download a JSON export
* @example Download a JSON file (embedded text resource)
* ```ts
* const data = JSON.stringify({ items: selectedItems }, null, 2);
* const { isError } = await app.downloadFile({
* filename: "export.json",
* content: data,
* mimeType: "application/json",
* contents: [{
* type: "resource",
* resource: {
* uri: "file:///export.json",
* mimeType: "application/json",
* text: data,
* },
* }],
* });
* if (isError) {
* console.warn("Download denied or cancelled");
* }
* ```
*
* @example Download binary content (base64)
* @example Download binary content (embedded blob resource)
* ```ts
* const { isError } = await app.downloadFile({
* filename: "image.png",
* content: base64EncodedPng,
* mimeType: "image/png",
* encoding: "base64",
* contents: [{
* type: "resource",
* resource: {
* uri: "file:///image.png",
* mimeType: "image/png",
* blob: base64EncodedPng,
* },
* }],
* });
* ```
*
* @example Download via resource link (host fetches)
* ```ts
* const { isError } = await app.downloadFile({
* contents: [{
* type: "resource_link",
* uri: "https://api.example.com/reports/q4.pdf",
* name: "Q4 Report",
* mimeType: "application/pdf",
* }],
* });
* ```
*