# api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs (RFC 9727) vs The 'knowledge-linkset' Well-Known URI for Publishing Knowledge Artefacts

The map lists them as complementary: sites and agents commonly implement both.

[1 Discover](/category/discover/) [api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs](/protocols/api-catalog-rfc9727/) · [1 Discover](/category/discover/) [The 'knowledge-linkset' Well-Known URI for Publishing Knowledge Artefacts](/protocols/knowledge-linkset/)

|  | [api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs](/protocols/api-catalog-rfc9727/) RFC 9727 | [The 'knowledge-linkset' Well-Known URI for Publishing Knowledge Artefacts](/protocols/knowledge-linkset/) |
| --- | --- | --- |
| Lifecycle step | 1 Discover: What is here, and where? | 1 Discover: What is here, and where? |
| Answers | Given a publisher's domain, where is the machine-readable list of the APIs it exposes? | How can a web origin publish, at one well-known location, a checkable list of the knowledge artefacts it offers (graph serializations, JSON-LD context, text file, chunk export, change ledger) so that agents can find them and verify digests? |
| Governed by | IETF; published as a Standards Track RFC with the IETF as change controller | Individual Internet-Draft, not adopted by a working group; Informational intended status; the artefact formats are defined in a separate AgenticSystemCore Specification. |
| Status (issuer's words) | Proposed Standard (errata exist) | Internet-Draft, Intended Status: Informational; expires 17 April 2027; work in progress |
| Version | RFC 9727 (2025-06) | draft-besleaga-agentic-knowledge-wellknown-01 (2026-10-14) |
| Form / transport | well-known file | well-known file |
| Found at | /.well-known/api-catalog | /.well-known/knowledge-linkset |
| Implementation | multi-implementation | none found |
| Evidence | 2 verified | 1 reported |
| Primary use case | Let agents discover my API or service | Serve readable content to agents |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | [https://www.rfc-editor.org/rfc/rfc9727.html](https://www.rfc-editor.org/rfc/rfc9727.html) | [https://datatracker.ietf.org/doc/html/draft-besleaga-agentic-knowledge-wellknown-01](https://datatracker.ietf.org/doc/html/draft-besleaga-agentic-knowledge-wellknown-01) |

## When to use which

- Choose api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs when your question is “Given a publisher's domain, where is the machine-readable list of the APIs it exposes?” and you accept its maturity: status "Proposed Standard (errata exist)", implementation multi-implementation.
- Choose The 'knowledge-linkset' Well-Known URI for Publishing Knowledge Artefacts when your question is “How can a web origin publish, at one well-known location, a checkable list of the knowledge artefacts it offers (graph serializations, JSON-LD context, text file, chunk export, change ledger) so that agents can find them and verify digests?” and you accept its maturity: status "Internet-Draft, Intended Status: Informational; expires 17 April 2027; work in progress", implementation none found.

Guidance is derived from the two records (question, status, implementation, prerequisites, pairings), not from opinion. Each record's page carries its numbered references.

## Read the full articles

- [api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs](/protocols/api-catalog-rfc9727/): Given a publisher's domain, where is the machine-readable list of the APIs it exposes?
- [The 'knowledge-linkset' Well-Known URI for Publishing Knowledge Artefacts](/protocols/knowledge-linkset/): How can a web origin publish, at one well-known location, a checkable list of the knowledge artefacts it offers (graph serializations, JSON-LD context, text file, chunk export, change ledger) so that agents can find them and verify digests?

Ask the MCP server to compare any two: the compare-protocols prompt, or get on both ids. [Connect](/connect/).

[api-catalog-rfc9727.json](/data/protocols/api-catalog-rfc9727.json) · [knowledge-linkset.json](/data/protocols/knowledge-linkset.json) · [Markdown](/compare/api-catalog-rfc9727-vs-knowledge-linkset/index.md)