Clarify server behavior if content type is not supported

apis/beacon/blob_sidecars/blob_sidecars.yaml

@@ -68,5 +68,7 @@ get:
           example:
             code: 404
             message: "Block not found"
+    "406":
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/beacon/blocks/blinded_block.yaml

@@ -60,5 +60,7 @@ get:
           example:
             code: 404
             message: "Block not found"
+    "406":
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/beacon/blocks/block.v2.yaml

@@ -41,7 +41,6 @@ get:
                   - $ref: "../../../beacon-node-oapi.yaml#/components/schemas/Deneb.SignedBeaconBlock"
         application/octet-stream:
           schema:
-
             description: "SSZ serialized block bytes. Use Accept header to choose this response type"
     "400":
       description: "The block ID supplied could not be parsed"
@@ -61,5 +60,7 @@ get:
           example:
             code: 404
             message: "Block not found"
+    "406":
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/beacon/deposit_snapshot.yaml

@@ -3,7 +3,7 @@
     summary: "Get Deposit Tree Snapshot"
     description: |
       Retrieve [EIP-4881](https://eips.ethereum.org/EIPS/eip-4881) Deposit Tree Snapshot.
-      Depending on `Accept` header it can be returned either as json or as bytes serialzed by SSZ
+      Depending on `Accept` header it can be returned either as json or as bytes serialized by SSZ
     tags:
       - Beacon
     responses:
@@ -30,5 +30,7 @@
             example:
               code: 404
               message: "No Finalized Snapshot Available"
+      "406":
+        $ref: "../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
       "500":
         $ref: '../../beacon-node-oapi.yaml#/components/responses/InternalError'

apis/beacon/light_client/bootstrap.yaml

@@ -54,13 +54,6 @@ get:
             code: 404
             message: "LC bootstrap unavailable"
     "406":
-      description: Unacceptable media type
-      content:
-        application/json:
-          schema:
-            $ref: "../../../beacon-node-oapi.yaml#/components/schemas/ErrorMessage"
-          example:
-            code: 406
-            message: "Accepted media type not supported"
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/beacon/light_client/finality_update.yaml

@@ -40,13 +40,6 @@ get:
             code: 404
             message: "LC finality update unavailable"
     "406":
-      description: Unacceptable media type
-      content:
-        application/json:
-          schema:
-            $ref: "../../../beacon-node-oapi.yaml#/components/schemas/ErrorMessage"
-          example:
-            code: 406
-            message: "Accepted media type not supported"
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/beacon/light_client/optimistic_update.yaml

@@ -40,13 +40,6 @@ get:
             code: 404
             message: "LC optimistic update unavailable"
     "406":
-      description: Unacceptable media type
-      content:
-        application/json:
-          schema:
-            $ref: "../../../beacon-node-oapi.yaml#/components/schemas/ErrorMessage"
-          example:
-            code: 406
-            message: "Accepted media type not supported"
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/beacon/light_client/updates.yaml

@@ -85,13 +85,6 @@ get:
                 code: 400
                 message: "Missing `count` value"
     "406":
-      description: Unacceptable media type
-      content:
-        application/json:
-          schema:
-            $ref: "../../../beacon-node-oapi.yaml#/components/schemas/ErrorMessage"
-          example:
-            code: 406
-            message: "Accepted media type not supported"
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: "../../../beacon-node-oapi.yaml#/components/responses/InternalError"

apis/builder/states/expected_withdrawals.yaml

@@ -56,5 +56,7 @@ get:
           example:
             code: 404
             message: "State not found"
+    "406":
+      $ref: "../../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: '../../../beacon-node-oapi.yaml#/components/responses/InternalError'

apis/debug/state.v2.yaml

@@ -60,6 +60,8 @@ get:
           example:
             code: 404
             message: "State not found"
+    "406":
+      $ref: "../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: '../../beacon-node-oapi.yaml#/components/responses/InternalError'
 

apis/validator/blinded_block.yaml

@@ -72,6 +72,8 @@ get:
               value:
                 code: 400
                 message: "Invalid request to produce a block"
+    "406":
+      $ref: "../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: '../../beacon-node-oapi.yaml#/components/responses/InternalError'
     "503":

apis/validator/block.v2.yaml

@@ -69,6 +69,8 @@ get:
               value:
                 code: 400
                 message: "Invalid request to produce a block"
+    "406":
+      $ref: "../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: '../../beacon-node-oapi.yaml#/components/responses/InternalError'
     "503":

apis/validator/block.v3.yaml

@@ -125,6 +125,8 @@ get:
               value:
                 code: 400
                 message: "Invalid request to produce a block"
+    "406":
+      $ref: "../../beacon-node-oapi.yaml#/components/responses/NotAcceptable"
     "500":
       $ref: '../../beacon-node-oapi.yaml#/components/responses/InternalError'
     "503":

beacon-node-oapi.yaml

@@ -6,9 +6,15 @@ info:
     API specification for the beacon node, which enables users to query and participate in Ethereum 2.0 phase 0 beacon chain.
 
     All requests by default send and receive JSON, and as such should have either or both of the "Content-Type: application/json"
-    and "Accept: application/json" headers.  In addition, some requests can return data in the SSZ format.  To indicate that SSZ
-    data is required in response to a request the header "Accept: application/octet-stream" should be sent.  Note that only a subset
-    of requests can respond with data in SSZ format; these are noted in each individual request.
+    and "Accept: application/json" headers.  In addition, some requests can send and receive data in the SSZ format.  The header
+    "Content-Type: application/octet-stream" should be set in requests that contain SSZ data; a preference to receive SSZ data in
+    response can be indicated by setting the "Accept: application/octet-stream;q=1.0,application/json;q=0.9" header.  Note that
+    only a subset of requests can respond with data in SSZ format; these are noted in each individual request.
+
+    When handling requests, the server should return a 415 status code if the "Content-Type" header in the request specifies a format
+    that is not supported.  Similarly, it should return a 406 status code if it cannot produce a response in the format accepted by
+    the client as specified in the "Accept" header; if no "Accept" header is provided then it is assumed to be "application/json".
+    In any case, the server should indicate the format of the response by setting the corresponding "Content-Type" header.
 
     API endpoints are individually versioned.  As such, there is no direct relationship between all v1 endpoints, all v2 endpoints,
     _etc._ and no such relationship should be inferred.  All JSON responses return the requested data under a `data` key in the top
@@ -413,6 +419,8 @@ components:
       $ref: './types/http.yaml#/InvalidRequest'
     NotFound:
       $ref: './types/http.yaml#/NotFound'
+    NotAcceptable:
+      $ref: './types/http.yaml#/NotAcceptable'
     UnsupportedMediaType:
       $ref: './types/http.yaml#/UnsupportedMediaType'
     InternalError:

types/http.yaml

@@ -110,16 +110,39 @@ NotFound:
       example:
         code: 404
         message: "Requested item not found"
+NotAcceptable:
+  description: "Accepted media type is not supported."
+  content:
+    application/json:
+      schema:
+        type: object
+        required: [code, message]
+        properties:
+          code:
+            description: "The media type in \"Accept\" header is unsupported, and the request has been rejected. This occurs when the server cannot produce a response in the format accepted by the client."
+            type: number
+            example: 406
+          message:
+            description: "Message describing error"
+            type: string
+          stacktraces:
+            description: "Optional stacktraces, sent when node is in debug mode"
+            type: array
+            items:
+              type: string
+      example:
+        code: 406
+        message: "Accepted media type not supported"
 UnsupportedMediaType:
-  description: "The supplied content-type is not supported."
+  description: "Supplied content-type is not supported."
   content:
     application/json:
       schema:
         type: object
         required: [code, message]
         properties:
           code:
-            description: "The media type supplied is unsupported, and the request has been rejected. This occurs when a HTTP request supplies a payload in a content-type that the service is not able to accept."
+            description: "The media type in \"Content-Type\" header is unsupported, and the request has been rejected. This occurs when a HTTP request supplies a payload in a content-type that the server is not able to handle."
             type: number
             example: 415
           message: