From 865a7376e312222056a4cb5b494daffb5696d19c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?St=C3=A9phane=20Tailland?= Date: Sat, 29 Aug 2026 12:19:31 +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 | 85 +++++++++++++++++++++++--------------- 1 file changed, 51 insertions(+), 34 deletions(-) diff --git a/kong/mcp/ai-mcp-proxy.yaml b/kong/mcp/ai-mcp-proxy.yaml index 692a9e4..19b9973 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: @@ -93,33 +95,38 @@ config: type: string maxLength: 50 addressline2: - type: string - nullable: true + type: + - string + - 'null' maxLength: 50 city: type: string maxLength: 50 state: - type: string - nullable: true + type: + - string + - 'null' maxLength: 50 postalcode: - type: string - nullable: true + type: + - string + - 'null' maxLength: 15 country: type: string maxLength: 50 creditlimit: - type: string + type: + - string + - 'null' format: decimal pattern: ^-?\d{0,8}(?:\.\d{0,2})?$ - nullable: true salesrepemployeenumber: - type: integer + type: + - integer + - 'null' maximum: 2147483647 minimum: -2147483648 - nullable: true required: - addressline1 - city @@ -183,33 +190,38 @@ config: type: string maxLength: 50 addressline2: - type: string - nullable: true + type: + - string + - 'null' maxLength: 50 city: type: string maxLength: 50 state: - type: string - nullable: true + type: + - string + - 'null' maxLength: 50 postalcode: - type: string - nullable: true + type: + - string + - 'null' maxLength: 15 country: type: string maxLength: 50 creditlimit: - type: string + type: + - string + - 'null' format: decimal pattern: ^-?\d{0,8}(?:\.\d{0,2})?$ - nullable: true salesrepemployeenumber: - type: integer + type: + - integer + - 'null' maximum: 2147483647 minimum: -2147483648 - nullable: true required: - addressline1 - city @@ -304,33 +316,38 @@ config: type: string maxLength: 50 addressline2: - type: string - nullable: true + type: + - string + - 'null' maxLength: 50 city: type: string maxLength: 50 state: - type: string - nullable: true + type: + - string + - 'null' maxLength: 50 postalcode: - type: string - nullable: true + type: + - string + - 'null' maxLength: 15 country: type: string maxLength: 50 creditlimit: - type: string + type: + - string + - 'null' format: decimal pattern: ^-?\d{0,8}(?:\.\d{0,2})?$ - nullable: true salesrepemployeenumber: - type: integer + type: + - integer + - 'null' maximum: 2147483647 minimum: -2147483648 - nullable: true required: - addressline1 - city