OpenAPI vs MCP
Product engineer: Keep the OpenAPI file and link it; agents reach it through links (Ora lab, 8 Oct 2026). Developer-platform lead: An OpenAPI file can seed MCP tools through gateways such as Kong. Agent builder: MCP gives you auth discovery; OpenAPI does not.
The sourced difference
OpenAPI describes endpoints for code generation; MCP serves tool descriptions written for models and handles auth discovery through RFC 9728 metadata. (OpenAPI: OpenAPI Specification (latest), read 5 November 2026; MCP: MCP authorization, 2026-07-28, read 5 November 2026)
Verdicts by reader
| Reader | Verdict |
|---|---|
| Product engineer | Keep the OpenAPI file and link it; agents reach it through links (Ora lab, 8 Oct 2026). |
| Developer-platform lead | An OpenAPI file can seed MCP tools through gateways such as Kong. |
| Agent builder | MCP gives you auth discovery; OpenAPI does not. |
Side by side
| Aspect | OpenAPI | MCP |
|---|---|---|
| Maintainer | OpenAPI Initiative (spec); each vendor for its own file | MCP maintainers under the Agentic AI Foundation |
| What it is | A machine-readable description of an HTTP API that agents and tool generators read to call endpoints without an MCP server. | A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation. |
| Status and version | OpenAPI 3.x in wide use; agents.json and Kong's AI MCP Server build on it. | Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025. |
| What it does not do | Does not carry agent auth flows or tool descriptions written for models; agents must find the file, usually through a link. | Does not grade servers, verify registry entries, or prescribe a .well-known discovery file in the 2026-07-28 core spec; server cards are still Working Group work. |
Read the full entries: OpenAPI and MCP.
Seen in the shared crawl
| Path | Top 10,000 found | Ora leaderboard found |
|---|---|---|
/openapi.json | 21 of 7,472 (0.28%) | 78 of 3,369 (2.32%) |
/openapi.yaml | 10 of 7,503 (0.13%) | 22 of 3,378 (0.65%) |
A path counts only when the answer is the right kind of document. Many sites answer these paths with an ordinary web page, which is not counted. See the census.
| Path | Top 10,000 found | Ora leaderboard found |
|---|---|---|
/.well-known/mcp.json | 19 of 7,470 (0.25%) | 66 of 3,366 (1.96%) |