From 644c013edfc6faeb4c976ae2d17724eb3d2e38c8 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?St=C3=A9phane=20Tailland?= Date: Sat, 29 Aug 2026 12:19:29 +0200 Subject: [PATCH] fix(mcp): translate OpenAPI 3.0 nullable into JSON Schema MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The response schemas added yesterday made every paginated list tool fail. The plugin's fields are documented as OpenAPI format and validated with a JSON Schema validator, and `nullable: true` is not a JSON Schema keyword — so it is ignored, `type: string` is enforced, and `previous: null` on the first page is rejected as *null is not of type "string"*. The failure lands after the backend has already done the work, surfaces to the caller as a bare tool retry exhaustion, and appears nowhere in the gateway's own logs. Found only because an orchestrating agent asked a question that paged. The generator now rewrites `nullable: true` into `type: [T, "null"]` wherever it inlines a schema, request bodies included. A 3.1 spec needs none of this. Co-Authored-By: Claude Opus 5 --- kong/mcp/ai-mcp-proxy.yaml | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kong/mcp/ai-mcp-proxy.yaml b/kong/mcp/ai-mcp-proxy.yaml index a214f9e..2502f94 100644 --- a/kong/mcp/ai-mcp-proxy.yaml +++ b/kong/mcp/ai-mcp-proxy.yaml @@ -58,13 +58,15 @@ config: type: integer example: 123 next: - type: string - nullable: true + type: + - string + - 'null' format: uri example: http://api.example.org/accounts/?page=4 previous: - type: string - nullable: true + type: + - string + - 'null' format: uri example: http://api.example.org/accounts/?page=2 results: