Glossary · Protocols and standards
NLWeb
An open project from Microsoft that gives a website a natural-language query endpoint answering in Schema.org JSON. Every instance is also an MCP server.
NLWeb (short for Natural Language Web) is an open project from Microsoft that lets a website answer natural-language questions about its own content through a simple API, returning results as Schema.org-typed JSON.
Origin. Microsoft introduced NLWeb in 2025. It was conceived and developed by R.V. Guha, who created RSS, RDF and Schema.org. NLWeb has two parts: a small protocol for asking a site questions in natural language, and an MIT-licensed Python reference implementation, now maintained at github.com/nlweb-ai/NLWeb.
How it works. NLWeb builds on structured data that sites already publish, such as Schema.org markup and RSS feeds. The implementation loads that data into a vector store and combines it with a language model of the operator’s choice. It exposes two endpoints that take the same arguments:
/askreturns results for web clients and apps./mcpreturns results in the format MCP clients expect, and also supports the core MCP methods for listing and calling tools and prompts.
The only required argument is query. Optional arguments include site (a subset of the backend’s data), prev (earlier queries in the conversation), mode and streaming. The mode can be list (top matches), summarize (a summary plus the list) or generate (an answer built with the model, closer to retrieval-augmented generation). The reference server keeps no conversation state, so the client sends context back with each request. Each result carries a url, name, site, score, a generated description, and the item’s own Schema.org object.
Where it sits. The project describes NLWeb as the content layer that agent protocols carry, and compares the pairing to HTML over HTTP. Every instance is an MCP server today, and the README lists A2A support as planned. NLWeb answers questions about a site’s content. A2A, by contrast, is for delegating tasks between independent agents.
Neighbouring terms. MCP connects an agent to tools and data, and an NLWeb site is one such data source. An Agent Card describes an A2A agent’s skills in a similar machine-readable way.