github/github-mcp-server · error

field_name is required for each issue_fields item

Error message

field_name is required for each issue_fields item

What it means

optionalIssueWriteFields (pkg/github/issues.go:260) requires every issue_fields item to carry a non-blank field_name. This error fires when an item omits field_name, or its value is empty/whitespace-only (the code trims before checking). It is a pure input-validation failure; no API call is made.

Source

Thrown at pkg/github/issues.go:260

	case []any:
		for _, item := range v {
			itemMap, ok := item.(map[string]any)
			if !ok {
				return nil, fmt.Errorf("each issue_fields item must be an object")
			}
			inputMaps = append(inputMaps, itemMap)
		}
	case []map[string]any:
		inputMaps = v
	default:
		return nil, fmt.Errorf("issue_fields must be an array")
	}

	issueFields := make([]issueWriteFieldInput, 0, len(inputMaps))
	for _, itemMap := range inputMaps {
		fieldName, err := RequiredParam[string](itemMap, "field_name")
		if err != nil || strings.TrimSpace(fieldName) == "" {
			return nil, fmt.Errorf("field_name is required for each issue_fields item")
		}

		fieldOptionName, err := OptionalParam[string](itemMap, "field_option_name")
		if err != nil {
			return nil, err
		}

		deleteField, _ := OptionalParam[bool](itemMap, "delete")
		value, hasValue := itemMap["value"]
		if hasValue && value == nil {
			return nil, fmt.Errorf("value cannot be null for field %q", fieldName)
		}

		if deleteField {
			if hasValue || fieldOptionName != "" {
				return nil, fmt.Errorf("issue field %q cannot specify 'delete' together with 'value' or 'field_option_name'", fieldName)
			}
			issueFields = append(issueFields, issueWriteFieldInput{

View on GitHub (pinned to 0ea1f775a7)

Solutions

1. Add field_name with the exact name shown in the repository's issue-fields settings: {"field_name":"Priority",...}
2. Use snake_case keys exactly as defined by the tool schema
3. Trim check: a whitespace-only name is rejected — supply the real name

Example fix

# before
{"issue_fields": [{"value": "P0"}]}

# after
{"issue_fields": [{"field_name": "Priority", "field_option_name": "P0"}]}

for _, item := range inputMaps {
    name, ok := item["field_name"].(string)
    if !ok || strings.TrimSpace(name) == "" {
        return errors.New("field_name is required for each issue_fields item")
    }
}

func hasFieldName(item map[string]any) bool {
    s, ok := item["field_name"].(string)
    return ok && strings.TrimSpace(s) != ""
}

When it happens

Trigger: update_issue issue_fields item like {"value":"P0"} (field_name missing) or {"field_name":" ","value":"P0"}. Also fires when RequiredParam[string] itself errors because field_name is a non-string JSON type (number, object).

Common situations: Agents guessing the option-name as field_name; typos like fieldname/fieldName (schema is snake_case); copy-paste payloads missing the key.

Related errors

• each issue_fields item must be an object
• issue_fields must be an array
• value cannot be null for field %q
• issue field %q cannot specify 'delete' together with 'value'
• issue field %q cannot specify both value and field_option_na

AI-assisted analysis of github/github-mcp-server@0ea1f775a7 (2026-08-15). Data as JSON: /api/errors/e6e974b4b8effdd7. Report an issue: GitHub.