WebMCP vs agents.json
The map lists them as complementary: sites and agents commonly implement both.
| WebMCP | agents.json | |
|---|---|---|
| Lifecycle step | 5 Act: Do something for me | 5 Act: Do something for me |
| Answers | What JavaScript tools can a web page register so an in-browser AI agent can call them directly instead of scraping the DOM? | How does an agent learn which multi-step API call sequences ("flows") a service supports, on top of its raw OpenAPI surface? |
| Governed by | W3C Web Machine Learning Community Group; editors are Brandon Walderman (Microsoft), Khushal Sagar (Google), Dominic Farolino (Google) | Wildcard AI; single company controls the spec and the reference "Wildcard Bridge" runtime and maintains a discretionary registry of published files |
| Status (issuer's words) | Draft Community Group Report, dated 4 September 2026; explicitly "not a W3C Standard nor on the W3C Standards Track" | Dormant: last push 2025-08-21, version 0.1.0 |
| Version | Draft Community Group Report, 4 September 2026 (2026-09-04) | 0.1.0 (2025-03) |
| Form / transport | browser API | well-known file |
| Found at | none — a client or agent must load the page itself to see whether it registers WebMCP tools; this is a stated limitation of the API ("Clients and browsers must visit a site directly to know if it has callable tools") | /.well-known/agents.json (proposed; not mandatory, per the spec's own FAQ) |
| Implementation | prototype | prototype |
| Evidence | 2 verified | 4 verified, 2 reported |
| Primary use case | Let agents act on my website | Let agents discover my API or service |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | https://webmachinelearning.github.io/webmcp/ | https://github.com/wild-card-ai/agents-json |
When to use which
- Choose WebMCP when your question is “What JavaScript tools can a web page register so an in-browser AI agent can call them directly instead of scraping the DOM?” and you accept its maturity: status "Draft Community Group Report, dated 4 September 2026; explicitly "not a W3C Standard nor on the W3C Standards Track"", implementation prototype.
- Choose agents.json when your question is “How does an agent learn which multi-step API call sequences ("flows") a service supports, on top of its raw OpenAPI surface?” and you accept its maturity: status "Dormant: last push 2025-08-21, version 0.1.0", implementation prototype. It is no longer maintained; prefer its successor.
Read the full articles
- WebMCP: What JavaScript tools can a web page register so an in-browser AI agent can call them directly instead of scraping the DOM?
- agents.json: How does an agent learn which multi-step API call sequences ("flows") a service supports, on top of its raw OpenAPI surface?