Hermes Adds Perplexity as a Backend for Its Web Tools

Hermes Agent can now use Perplexity as the backend for its existing web search and page-extraction tools without changing the model it uses for reasoning and writing. The new option creates a clean split between retrieval and the agent model, but it comes with an evidence boundary: extraction returns relevant passages, not a complete copy of a source page.

The provider is included in Hermes v0.21.1 and later; v0.21.0 does not include it. Users can keep their current model provider for reasoning and writing while configuring a separate Perplexity API key for search and extraction.

One agent, separate jobs

The change affects Hermes’s web tools rather than the model running the agent. Hermes sends requests to Perplexity directly over HTTP, so the setup does not require Perplexity’s SDK, command-line interface, or an MCP server.

Relevant text can still be incomplete

Hermes limits Perplexity search requests to 20 results and uses short search context for result descriptions. Extraction works differently: it returns selected material relevant to a URL, which can leave out details found on the original page.

That distinction matters when an agent is asked to make a source-grounded claim. Perplexity’s documentation gives an example in which an extract preserves a reference to “the new function” but omits the function’s name. The missing name is not established by the retrieved excerpt, so it should not be supplied from memory or guesswork.

Old settings can override the new backend

Hermes offers a tools setup wizard as well as manual configuration. For existing installations, search-specific and extraction-specific settings take precedence over the shared web backend, so adding an API key alone may not redirect either tool to Perplexity.

web:
  backend: perplexity
  search_backend: perplexity
  extract_backend: perplexity

Perplexity recommends disabling caching and keyless fallback during testing. Otherwise, a cached response or another provider could satisfy a request after a Perplexity error; a meaningful check shows a web_search call and usable returned results.