mcp-validation-response (#589)

* mcp-validation-response

Summary:

- Added `valid` key to `validate_query_json_v2`, per contract.
- Amended robot test `MCP HTTPS Server Validate Canonical`.
- Added robot test `MCP HTTPS Server Validate Canonical Negative`.

* - Corrrected keyword usage.

Author: general-kroll-4-life

pkg/mcp_server/dto/dto.go

@@ -181,6 +181,12 @@ type QueryResultDTO struct {
 	Warnings []string         `json:"warnings,omitempty"`
 }
 
+type ValidationResultDTO struct {
+	IsValid bool     `json:"valid"`
+	Message string   `json:"message,omitempty"`
+	Errors  []string `json:"errors,omitempty"`
+}
+
 // GreetDTO carries a simple greeting payload.
 type GreetDTO struct {
 	Greeting string `json:"greeting"`

pkg/mcp_server/server.go

@@ -231,10 +231,15 @@ func newMCPServer(config *Config, backend Backend, logger *logrus.Logger) (MCPSe
 		},
 		func(ctx context.Context, req *mcp.CallToolRequest, args dto.QueryJSONInput) (*mcp.CallToolResult, any, error) {
 			arr, err := backend.ValidateQuery(ctx, args.SQL)
+			isValid := err == nil
+			message := "Query validation succeeded."
+			var errorsToPublish []string
 			if err != nil {
-				return nil, nil, err
+				errorsToPublish = append(errorsToPublish, err.Error())
+				arrBytes, _ := json.Marshal(arr)
+				message = fmt.Sprintf("Query validation failed, returned data: %s", string(arrBytes))
 			}
-			out := dto.QueryResultDTO{Rows: arr, RowCount: len(arr), Format: "json"}
+			out := dto.ValidationResultDTO{IsValid: isValid, Errors: errorsToPublish, Message: message}
 			bytesOut, _ := json.Marshal(out)
 			return &mcp.CallToolResult{Content: []mcp.Content{&mcp.TextContent{Text: string(bytesOut)}}}, out, nil
 		},

test/robot/functional/mcp.robot

@@ -1,6 +1,7 @@
 *** Settings ***
 Resource          ${CURDIR}${/}stackql.resource
 Library           Collections
+Library           Builtin
 
 
 *** Keywords ***
@@ -523,8 +524,28 @@ MCP HTTPS Server Validate Canonical
     ...    stdout=${CURDIR}${/}tmp${/}MCP-HTTPS-validate-canonical.txt
     ...    stderr=${CURDIR}${/}tmp${/}MCP-HTTPS-validate-canonical-stderr.txt
     ${meta_rels_obj}=    Parse MCP JSON Output    ${meta_rels.stdout}
-    Dictionary Should Contain Key    ${meta_rels_obj}    rows
-    Length Should Be    ${meta_rels_obj['rows']}    1
+    Dictionary Should Contain Key    ${meta_rels_obj}    valid
+    Should Be True                   ${meta_rels_obj}[valid]
+
+MCP HTTPS Server Validate Canonical Negative
+    Pass Execution If    "%{IS_SKIP_MCP_TEST=false}" == "true"    Some platforms do not have the MCP client available
+    # Future proofing: raw text format reserved; may gain structured hints later.
+    ${meta_rels}=    Run Process
+    ...    ${STACKQL_MCP_CLIENT_EXE}
+    ...    exec
+    ...    \-\-client\-type\=http
+    ...    \-\-url\=https://127.0.0.1:9004
+    ...    \-\-client\-cfg
+    ...    { "apply_tls_globally": true, "insecure_skip_verify": true, "ca_file": "test/server/mtls/credentials/pg_server_cert.pem", "promote_leaf_to_ca": true }
+    ...    \-\-exec.action
+    ...    validate_query_json_v2
+    ...    \-\-exec.args
+    ...    {"sql":"select * from google.storage.buckets2 where project \= 'stackql\-demo';"}
+    ...    stdout=${CURDIR}${/}tmp${/}MCP-HTTPS-validate-canonical-negative.txt
+    ...    stderr=${CURDIR}${/}tmp${/}MCP-HTTPS-validate-canonical-negative-stderr.txt
+    ${meta_rels_obj}=    Parse MCP JSON Output    ${meta_rels.stdout}
+    Dictionary Should Contain Key    ${meta_rels_obj}    valid
+    Should Be True                   ${meta_rels_obj}[valid] == False
 
 MCP HTTPS Server Query Canonical
     Pass Execution If    "%{IS_SKIP_MCP_TEST=false}" == "true"    Some platforms do not have the MCP client available