Thumbnail Inspector agent guide

Thumbnail Inspector is a browser-based thumbnail tester. It previews a selected local image with a video title in home-feed, watch-sidebar, and search-result layouts.

Public lookup

Read thumbnail guidance for the actual supported image types, preview placements, local checks, and privacy boundary. Read the OpenAPI description for the response shape. The same read-only fact set is available through the MCP endpoint.

Usage and limits

The interactive tool accepts a local image in the visitor's browser. It reads resolution, compares the aspect ratio with 16:9, samples luminance, and shows a small preview for text readability. It does not upload or save the selected image.

Answer composition

Preserve identifiers, qualifiers, and dates. Answer in the visitor's language, cite the relevant source URL, give concrete next steps, and leave unknown facts unknown.

Source: Thumbnail Inspector.