Compatibility matrix
A claim of support needs a source and a scope. This matrix separates what a publisher can implement from what a client has documented or what a dated observation has measured.
Last updated:
Evidence classes
| Capability | What can be verified | What it does not prove |
|---|---|---|
/llms.txt publication | HTTP response, content type and file syntax can be checked live. | Automatic client discovery or impact on an AI answer. |
| Markdown alternate | A page can expose rel="alternate" type="text/markdown". | That any named tool fetches it. |
describedby | The relation can be present in HTML or an HTTP Link header. | Universal v2 support or a ranking signal. |
| Client behavior | Provider documentation or a reproducible, scoped test. | Behavior of another client or a future version. |
Current observatory baseline
In the current fixed-panel discovery observation, 28 pages exposed a
Markdown alternate and 4 exposed describedby. This is a
publication baseline, not a client leaderboard. The raw figures and limits are in the Observatory.
How to use the matrix
- Implement a capability you can maintain and verify.
- Link to the source that describes any client claim.
- Use unknown when neither a source nor a reproducible observation exists.
- Recheck claims after a product or specification release.