Support removing issue types

README.md

@@ -926,7 +926,7 @@ The following sets of tools are available:
   - **Required OAuth Scopes**: `repo`
   - `assignees`: Usernames to assign to this issue (string[], optional)
   - `body`: Issue body content (string, optional)
-  - `duplicate_of`: Issue number that this issue is a duplicate of. Only used when state_reason is 'duplicate'. (number, optional)
+  - `duplicate_of`: Issue number that this issue is a duplicate of. Required when state_reason is 'duplicate'. (number, optional)
   - `issue_fields`: Issue field values to set or clear. Each item requires 'field_name' and exactly one of 'value', 'field_option_name', or 'delete: true'. (object[], optional)
   - `issue_number`: Issue number to update (number, optional)
   - `labels`: Labels to apply to this issue (string[], optional)
@@ -941,7 +941,7 @@ The following sets of tools are available:
   - `state`: New state (string, optional)
   - `state_reason`: Reason for the state change. Ignored unless state is changed. (string, optional)
   - `title`: Issue title (string, optional)
-  - `type`: Type of this issue. Only use if issue types are enabled for this repository. Use list_issue_types tool to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter. (string, optional)
+  - `type`: Type of this issue. For updates, pass null to remove the current type. Only use if issue types are enabled for this repository. Use list_issue_types to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter. (string | null, optional)
 
 - **list_issue_fields** - List issue fields
   - **Required OAuth Scopes (any of)**: `repo`, `read:org`

cmd/github-mcp-server/generate_docs.go

@@ -273,19 +273,7 @@ func writeToolDoc(buf *strings.Builder, tool inventory.ServerTool) {
 				requiredStr = "required"
 			}
 
-			var typeStr string
-
-			// Get the type and description
-			switch prop.Type {
-			case "array":
-				if prop.Items != nil {
-					typeStr = prop.Items.Type + "[]"
-				} else {
-					typeStr = "array"
-				}
-			default:
-				typeStr = prop.Type
-			}
+			typeStr := schemaTypeString(prop)
 
 			// Indent any continuation lines in the description to maintain markdown formatting
 			description := indentMultilineDescription(prop.Description, "    ")
@@ -300,6 +288,40 @@ func writeToolDoc(buf *strings.Builder, tool inventory.ServerTool) {
 	}
 }
 
+func schemaTypeString(schema *jsonschema.Schema) string {
+	switch {
+	case schema.Type == "array":
+		if schema.Items != nil {
+			return schema.Items.Type + "[]"
+		}
+		return "array"
+	case schema.Type != "":
+		return schema.Type
+	case len(schema.Types) > 0:
+		return strings.Join(schema.Types, " | ")
+	}
+
+	var union []*jsonschema.Schema
+	switch {
+	case len(schema.AnyOf) > 0:
+		union = schema.AnyOf
+	case len(schema.OneOf) > 0:
+		union = schema.OneOf
+	default:
+		// A schema without type constraints accepts any value.
+		return "any"
+	}
+
+	types := make([]string, 0, len(union))
+	for _, member := range union {
+		memberType := schemaTypeString(member)
+		if !slices.Contains(types, memberType) {
+			types = append(types, memberType)
+		}
+	}
+	return strings.Join(types, " | ")
+}
+
 // scopesEqual checks if two scope slices contain the same elements (order-independent)
 func scopesEqual(a, b []string) bool {
 	if len(a) != len(b) {

cmd/github-mcp-server/main_test.go

@@ -5,6 +5,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/google/jsonschema-go/jsonschema"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -36,3 +37,29 @@ func TestGitHubAppFlagsAreStdioOnly(t *testing.T) {
 	assert.NotNil(t, stdioCmd.Flags().Lookup("app-id"))
 	assert.Nil(t, httpCmd.Flags().Lookup("app-id"))
 }
+
+func TestSchemaTypeString(t *testing.T) {
+	tests := []struct {
+		name   string
+		schema *jsonschema.Schema
+		want   string
+	}{
+		{name: "type", schema: &jsonschema.Schema{Type: "string"}, want: "string"},
+		{name: "types", schema: &jsonschema.Schema{Types: []string{"string", "number"}}, want: "string | number"},
+		{name: "unconstrained", schema: &jsonschema.Schema{}, want: "any"},
+		{name: "anyOf", schema: &jsonschema.Schema{AnyOf: []*jsonschema.Schema{{Type: "string"}, {Type: "null"}}}, want: "string | null"},
+		{name: "oneOf", schema: &jsonschema.Schema{OneOf: []*jsonschema.Schema{{Type: "number"}, {Type: "string"}}}, want: "number | string"},
+		{
+			name:   "array",
+			schema: &jsonschema.Schema{Type: "array", Items: &jsonschema.Schema{Type: "string"}},
+			want:   "string[]",
+		},
+		{name: "untyped array", schema: &jsonschema.Schema{Type: "array"}, want: "array"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.Equal(t, tc.want, schemaTypeString(tc.schema))
+		})
+	}
+}

docs/feature-flags.md

@@ -56,7 +56,7 @@ runtime behavior (such as output formatting) won't appear here.
   - **MCP App UI**: `ui://github-mcp-server/issue-write`
   - `assignees`: Usernames to assign to this issue (string[], optional)
   - `body`: Issue body content (string, optional)
-  - `duplicate_of`: Issue number that this issue is a duplicate of. Only used when state_reason is 'duplicate'. (number, optional)
+  - `duplicate_of`: Issue number that this issue is a duplicate of. Required when state_reason is 'duplicate'. (number, optional)
   - `issue_fields`: Issue field values to set or clear. Each item requires 'field_name' and exactly one of 'value', 'field_option_name', or 'delete: true'. (object[], optional)
   - `issue_number`: Issue number to update (number, optional)
   - `labels`: Labels to apply to this issue (string[], optional)
@@ -71,7 +71,7 @@ runtime behavior (such as output formatting) won't appear here.
   - `state`: New state (string, optional)
   - `state_reason`: Reason for the state change. Ignored unless state is changed. (string, optional)
   - `title`: Issue title (string, optional)
-  - `type`: Type of this issue. Only use if issue types are enabled for this repository. Use list_issue_types tool to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter. (string, optional)
+  - `type`: Type of this issue. For updates, pass null to remove the current type. Only use if issue types are enabled for this repository. Use list_issue_types to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter. (string | null, optional)
 
 - **ui_get** - Get UI data
   - **Required OAuth Scopes (any of)**: `repo`, `read:org`
@@ -200,7 +200,7 @@ runtime behavior (such as output formatting) won't appear here.
   - `confidence`: How confident you are in this choice. Use 'HIGH' for clear signal or explicit user request, 'MEDIUM' for reasonable inference with some ambiguity, 'LOW' for best guess with limited signal. (string, optional)
   - `is_suggestion`: If true, this issue type change is sent to the API as a suggestion (suggest:true) rather than an applied value. Whether the type is applied or recorded as a proposal is determined by the API. (boolean, optional)
   - `issue_number`: The issue number to update (number, required)
-  - `issue_type`: The issue type to set (string, required)
+  - `issue_type`: The issue type to set, or null to remove the current type (string | null, required)
   - `owner`: Repository owner (username or organization) (string, required)
   - `rationale`: One concise sentence explaining what specifically about the issue led you to choose this type. State the concrete signal (e.g. 'Reports a crash when saving' → bug, 'Asks for dark mode support' → feature). (string, optional)
   - `repo`: Repository name (string, required)

docs/insiders-features.md

@@ -50,7 +50,7 @@ The list below is generated from the Go source. It covers tool **inventory and s
   - **MCP App UI**: `ui://github-mcp-server/issue-write`
   - `assignees`: Usernames to assign to this issue (string[], optional)
   - `body`: Issue body content (string, optional)
-  - `duplicate_of`: Issue number that this issue is a duplicate of. Only used when state_reason is 'duplicate'. (number, optional)
+  - `duplicate_of`: Issue number that this issue is a duplicate of. Required when state_reason is 'duplicate'. (number, optional)
   - `issue_fields`: Issue field values to set or clear. Each item requires 'field_name' and exactly one of 'value', 'field_option_name', or 'delete: true'. (object[], optional)
   - `issue_number`: Issue number to update (number, optional)
   - `labels`: Labels to apply to this issue (string[], optional)
@@ -65,7 +65,7 @@ The list below is generated from the Go source. It covers tool **inventory and s
   - `state`: New state (string, optional)
   - `state_reason`: Reason for the state change. Ignored unless state is changed. (string, optional)
   - `title`: Issue title (string, optional)
-  - `type`: Type of this issue. Only use if issue types are enabled for this repository. Use list_issue_types tool to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter. (string, optional)
+  - `type`: Type of this issue. For updates, pass null to remove the current type. Only use if issue types are enabled for this repository. Use list_issue_types to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter. (string | null, optional)
 
 - **ui_get** - Get UI data
   - **Required OAuth Scopes (any of)**: `repo`, `read:org`

pkg/github/__toolsnaps__/issue_write.snap

@@ -28,7 +28,7 @@
         "type": "string"
       },
       "duplicate_of": {
-        "description": "Issue number that this issue is a duplicate of. Only used when state_reason is 'duplicate'.",
+        "description": "Issue number that this issue is a duplicate of. Required when state_reason is 'duplicate'.",
         "type": "number"
       },
       "issue_fields": {
@@ -120,8 +120,16 @@
         "type": "string"
       },
       "type": {
-        "description": "Type of this issue. Only use if issue types are enabled for this repository. Use list_issue_types tool to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter.",
-        "type": "string"
+        "anyOf": [
+          {
+            "minLength": 1,
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "Type of this issue. For updates, pass null to remove the current type. Only use if issue types are enabled for this repository. Use list_issue_types to get valid type values for this repository or its owner organization. If the repository doesn't support issue types, omit this parameter."
       }
     },
     "required": [

pkg/github/__toolsnaps__/update_issue_type.snap

@@ -6,7 +6,7 @@
     "readOnlyHint": false,
     "title": "Update Issue Type"
   },
-  "description": "Update the type of an existing issue (e.g. 'bug', 'feature'). When setting values, include a confidence level (LOW, MEDIUM, or HIGH) reflecting how certain you are about the choice.",
+  "description": "Set or remove the type of an existing issue. Pass null to remove the current type. When setting a value, include a confidence level (LOW, MEDIUM, or HIGH) reflecting how certain you are about the choice.",
   "inputSchema": {
     "properties": {
       "confidence": {
@@ -28,8 +28,16 @@
         "type": "number"
       },
       "issue_type": {
-        "description": "The issue type to set",
-        "type": "string"
+        "anyOf": [
+          {
+            "minLength": 1,
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ],
+        "description": "The issue type to set, or null to remove the current type"
       },
       "owner": {
         "description": "Repository owner (username or organization)",

pkg/github/granular_tools_test.go

@@ -3,6 +3,7 @@ package github
 import (
 	"context"
 	"encoding/json"
+	"maps"
 	"net/http"
 	"strings"
 	"testing"
@@ -787,6 +788,18 @@ func TestGranularUpdateIssueType(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "remove type with null",
+			requestArgs: map[string]any{
+				"owner":        "owner",
+				"repo":         "repo",
+				"issue_number": float64(1),
+				"issue_type":   nil,
+			},
+			expectedReq: map[string]any{
+				"type": nil,
+			},
+		},
 	}
 
 	for _, tc := range tests {
@@ -807,6 +820,45 @@ func TestGranularUpdateIssueType(t *testing.T) {
 	}
 }
 
+func TestGranularUpdateIssueTypeRejectsInvalidInput(t *testing.T) {
+	tests := []struct {
+		name      string
+		args      map[string]any
+		omitType  bool
+		wantError string
+	}{
+		{name: "missing type", omitType: true, wantError: "missing required parameter: issue_type"},
+		{name: "empty type", args: map[string]any{"issue_type": ""}, wantError: "parameter issue_type must not be empty"},
+		{name: "null with rationale", args: map[string]any{"rationale": "live validation"}, wantError: "suggestion metadata is not supported"},
+		{name: "null with confidence", args: map[string]any{"confidence": "HIGH"}, wantError: "suggestion metadata is not supported"},
+		{name: "null suggestion", args: map[string]any{"is_suggestion": true}, wantError: "suggestion metadata is not supported"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			deps := BaseDeps{}
+			serverTool := GranularUpdateIssueType(translations.NullTranslationHelper)
+			handler := serverTool.Handler(deps)
+			args := map[string]any{
+				"owner":        "owner",
+				"repo":         "repo",
+				"issue_number": float64(1),
+				"issue_type":   nil,
+			}
+			if tc.omitType {
+				delete(args, "issue_type")
+			}
+			maps.Copy(args, tc.args)
+			request := createMCPRequest(args)
+
+			result, err := handler(ContextWithDeps(context.Background(), deps), &request)
+			require.NoError(t, err)
+			errorContent := getErrorResult(t, result)
+			assert.Contains(t, errorContent.Text, tc.wantError)
+		})
+	}
+}
+
 func TestGranularUpdateIssueTypeSuggest(t *testing.T) {
 	tests := []struct {
 		name        string