How to add better web search to DeepSeek Harness: plugins and MCP setup

DeepSeek Harness (dsh), released as an MIT-licensed developer preview in August 2026, is a plugin-based agent harness built on Cordis that offers built-in web search and fetching but requires DeepSeek credentials for its default search provider and incurs the latency and token cost of an auxiliary model call per search. Users can alternatively install community plugins that preserve the native tool interface while adding different search engines, failover options, or specialized sources, though these plugins execute third-party code within the harness. dsh also includes an MCP client that can connect to external servers over stdio or Streamable HTTP, exposing their tools with an `mcp__<server>__<tool>` naming convention and allowing the same services to be reused across MCP-compatible applications. The text demonstrates configuring Parallel Search MCP through a YAML patch, which provides anonymous web search and multi-URL fetching without a DeepSeek key, while optional Parallel API credentials can increase rate limits and enable paid usage modes. It also covers persistent configuration locations, command-line flag ordering, tool discovery checks, disabling the built-in search tool in some profiles, timeout and connection troubleshooting, and the trade-offs between using plugins and MCP servers.

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