Troubleshooting & FAQ Leave feedback

Solutions to the most common GroupDocs.Viewer MCP server issues — server not appearing in the client, startup failures, missing native dependencies, and first-launch timeouts.

Note

Platform-specific troubleshooting: runtime problems depend on which build you run. For the dnx runner, native graphics libraries, and the Docker channel, see Troubleshooting (.NET). The issues on this page apply to every platform.

1. Restart the client — every client reads its MCP config only at startup.
2. Check the config file location for your OS (per-client reference) and that the entry sits under the right root key (mcpServers for Claude Desktop/Cursor/Windsurf, servers for VS Code/VS 2022).
3. Validate the JSON — a trailing comma silently breaks the whole file. If you used the installer, a timestamped .bak of your previous config sits next to the file for comparison.

A cold cache: on the very first use the server’s package or image is still downloading while the client is already waiting on the connection. Warming it once fixes it for good — the exact command depends on your build: .NET.

These are properties of the build you run rather than of MCP, so the fixes live with the platform:

Pass the file name, not a full path from your machine: the server resolves names inside its configured storage folder. When a name is not found the tool responds with the list of files it can see, so the agent can correct itself — check that list against GROUPDOCS_MCP_STORAGE_PATH.

render_page does not check the page number against the document. Asking for page 99 of a two-page PDF returns an image and saves it as <name>_page99.png, with no error. Ask for the page count first with get_view_info and render only pages that exist.

The server is running in evaluation mode. Every rendered page carries a watermark, and the response text starts with [Evaluation mode] Output may include watermarks. Check get_license_status and see Licensing.

In evaluation mode one server process opens at most 15 documents. After that, calls fail with an evaluation-cap error until the server restarts. Restart your AI client, or configure a licence.

Not through MCP today. render_page produces PNG only. The GroupDocs.Viewer library itself renders to HTML, JPG, PNG, and PDF — see the library documentation if you need those formats in your own code.

Each rendered page travels back inline as a PNG, typically a few hundred kilobytes of base64. Render the pages you need, not the whole document, and let the agent work from the saved files when it only needs to hand them on.

Ask your agent “list your GroupDocs Viewer tools and the license status” — it should name render_page, get_view_info, get_license_status. For a scripted check that performs the real MCP handshake and a live call through the engine, see verifying a .NET installation.

Post your config (redact license paths) and the client name in the Viewer forum — we answer MCP questions daily. Bugs: GitHub issues.