ai-plugin.json - the legacy OpenAI plugin manifest, now largely deprecated
Tests for the legacy /.well-known/ai-plugin.json manifest from the original OpenAI plugins era.
What this signal tests
We check for /.well-known/ai-plugin.json - the original OpenAI plugin manifest from 2023. It declares a schema version and an `api.url` pointing to an OpenAPI specification, so ChatGPT (in the plugins era) could install and call your service. The format has been largely superseded by GPTs and then by MCP, but the file is still present on many sites that built integrations in 2023.
Why it matters for your visibility in AI
We report this as historical context, not as a current best practice. OpenAI deprecated the plugins programme in 2024 and most modern AI integrations now happen through MCP (see our MCP signal) or vendor-specific connector frameworks. A present ai-plugin.json file no longer drives meaningful integration traffic for new users. That said, an existing ai-plugin.json signals historical investment in AI-readiness. It shows you were paying attention in 2023, you have an OpenAPI spec ready to go, and the migration to MCP is a short walk rather than a from-scratch build. If you have one, leaving it in place costs nothing. If you do not, building a new ai-plugin.json today is the wrong place to spend the effort - go straight to MCP instead. The consequence of failing this signal today is essentially zero. We test it because the file is part of the well-known URI registry and because its presence is useful context.
Pass criteria at a glance
| Criterion | Passes when |
|---|---|
| Valid manifest returned. |
How we test it
We send GET /.well-known/ai-plugin.json and check for a 200 response with valid JSON. The JSON must contain a `schema_version` field and an `api` object with a `url` pointing to your OpenAPI specification. We do not validate the OpenAPI spec itself - only that the manifest declares one. Content type is conventionally application/json. The well-known URI is registered at https://www.iana.org/assignments/well-known-uris/well-known-uris.xhtml.
Show technical detection method
GET /.well-known/ai-plugin.json; pass if 200 with schema_version + api.url.
If your site fails: how to fix it
- If you do not already have an ai-plugin.json, do not build one. The format is deprecated. Build an MCP server instead (see our MCP signal).
- If you have an existing ai-plugin.json from the 2023 plugins era and it still accurately describes a working OpenAPI endpoint, leave it in place - it costs nothing and signals historical investment.
- If your ai-plugin.json points to a broken or removed OpenAPI URL, either fix the URL or delete the manifest entirely - a 404 from a referenced API is worse than no manifest.
- Plan the migration path to MCP. The OpenAPI spec you already have is most of the work; an MCP server wraps it as agent-callable tools.
- Track the deprecation status in your tech-debt register. This signal will likely be removed from our catalogue in a future revision.
Quick facts
| Maturity | ESTABLISHED |
|---|---|
| Weight | low |
| Category | Emerging Standards |
Primary sources
Related signals
Frequently asked questions
Should I build a new ai-plugin.json today?
No. The format is deprecated. Any effort you would spend on a new ai-plugin.json belongs in an MCP server instead. We test for this signal mostly to provide context, not to recommend implementation.
Should I delete my existing ai-plugin.json?
Only if it points to a broken endpoint. A working ai-plugin.json is harmless and serves as documentation. A broken one (manifest exists, OpenAPI URL 404s) is worse than nothing - fix or remove.
Which AI systems honour ai-plugin.json today?
Essentially none in the consumer assistant space, since OpenAI shut down the plugins programme. A handful of legacy tooling and archive crawlers still parse it. Treat current adoption as near zero.
Will this still matter in two years?
Almost certainly less than today. We expect this signal to either be retired from our catalogue or reframed purely as a deprecation marker. MCP is the path forward.
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