Return images, audio, and binary/resource content from an MCP tool in TypeScript

Documented steps

1. A tool handler returns { content: [...] } where each block is a discriminated union on 'type': 'text' | 'image' | 'audio' | 'resource_link' | 'resource' — the same union prompt messages use. Defined in the SDK core schemas (ContentBlockSchema).
2. Image block: { type: 'image', data: '<base64 bytes, no data: prefix>', mimeType: 'image/png' } — both fields required. Example: return { content: [{ type: 'image', data: pngBuffer.toString('base64'), mimeType: 'image/png' }] };
3. Audio mirrors image: { type: 'audio', data: '<base64>', mimeType: 'audio/wav' }.
4. Embed resource bytes inline with type 'resource': { type: 'resource', resource: { uri: 'file:///chart.png', mimeType: 'image/png', blob: '<base64>' } } — resource contents carry either text or base64 blob, never both.
5. Point at a resource without inlining via resource_link: { type: 'resource_link', uri: 'file:///report.pdf', name: 'report', mimeType: 'application/pdf' }.
6. To make binary data readable via resources/read as well, register a resource: server.registerResource('chart', 'chart://latest', { title: 'Latest chart', mimeType: 'image/png' }, async (uri) => ({ contents: [{ uri: uri.href, mimeType: 'image/png', blob: chartPngBase64 }] })). Docs: https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/docs/servers/resources.md