feat(prebuilt/cloud-sql-mysql): Add env var support for IP Type (#1232) (#1347)

This PR fixes #1232 by allowing the `CLOUD_SQL_MYSQL_IP_TYPE`
environment variable to control the connection type for the
`cloud-sql-mysql` prebuilt tool, defaulting to "PUBLIC".

**Changes:**

* **`internal/prebuiltconfigs/tools/cloud-sql-mysql.yaml`:** Updated
`ipType` to use `${CLOUD_SQL_MYSQL_IP_TYPE:PUBLIC}`.
* **`internal/sources/cloudsqlmysql/cloud_sql_mysql.go`:** Removed
`validate:"required"` from the `IPType` field in the `Config` struct to
allow the default to be used when the env var is unset.
* **Documentation:** Updated relevant documentation to reflect the new
`CLOUD_SQL_MYSQL_IP_TYPE` environment variable usage.

**Testing:**

Built a local Docker image and tested on a GCE VM:

*   Setting `CLOUD_SQL_MYSQL_IP_TYPE="private"` connects via Private IP.
*   Setting `CLOUD_SQL_MYSQL_IP_TYPE="PUBLIC"` connects via Public IP.
*   Leaving `CLOUD_SQL_MYSQL_IP_TYPE` unset defaults to Public IP.

All tests initialized the toolbox successfully.

Fixes #1232



## Description

---
> Should include a concise description of the changes (bug or feature),
it's
> impact, along with a summary of the solution

## PR Checklist

---
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [ ] Make sure to add `!` if this involve a breaking change

🛠️ Fixes #1232

---------

Co-authored-by: Averi Kitsch <akitsch@google.com>

docs/en/reference/prebuilt-tools.md

@@ -75,6 +75,8 @@ See guides, [Connect from your IDE](../how-to/connect-ide/_index.md), for detail
     *   `CLOUD_SQL_MYSQL_DATABASE`: The name of the database to connect to.
     *   `CLOUD_SQL_MYSQL_USER`: The database username.
     *   `CLOUD_SQL_MYSQL_PASSWORD`: The password for the database user.
+    *   `CLOUD_SQL_MYSQL_IP_TYPE`: The IP type i.e. "Public
+     or "Private" (Default: Public).
 *   **Permissions:**
     *   **Cloud SQL Client** (`roles/cloudsql.client`) to connect to the instance.
     *   Database-level permissions (e.g., `SELECT`, `INSERT`) are required to execute queries.

internal/prebuiltconfigs/tools/cloud-sql-mysql.yaml

@@ -1,3 +1,17 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 sources:
   cloud-sql-mysql-source:
     kind: cloud-sql-mysql
@@ -7,6 +21,7 @@ sources:
     database: ${CLOUD_SQL_MYSQL_DATABASE}
     user: ${CLOUD_SQL_MYSQL_USER}
     password: ${CLOUD_SQL_MYSQL_PASSWORD}
+    ipType: ${CLOUD_SQL_MYSQL_IP_TYPE:PUBLIC}
 tools:
   execute_sql:
     kind: mysql-execute-sql

internal/sources/cloudsqlmysql/cloud_sql_mysql.go

@@ -52,7 +52,7 @@ type Config struct {
 	Project  string         `yaml:"project" validate:"required"`
 	Region   string         `yaml:"region" validate:"required"`
 	Instance string         `yaml:"instance" validate:"required"`
-	IPType   sources.IPType `yaml:"ipType" validate:"required"`
+	IPType   sources.IPType `yaml:"ipType"`
 	User     string         `yaml:"user" validate:"required"`
 	Password string         `yaml:"password" validate:"required"`
 	Database string         `yaml:"database" validate:"required"`

tests/common.go

@@ -23,6 +23,11 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/goccy/go-yaml"
+	"github.com/google/go-cmp/cmp"
+	"github.com/googleapis/genai-toolbox/internal/server"
+	"github.com/googleapis/genai-toolbox/internal/sources/cloudsqlmysql"
+	"github.com/googleapis/genai-toolbox/internal/testutils"
 	"github.com/googleapis/genai-toolbox/internal/tools"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
@@ -645,3 +650,112 @@ func GetRedisValkeyToolsConfig(sourceConfig map[string]any, toolKind string) map
 	}
 	return toolsFile
 }
+
+// TestCloudSQLMySQL_IPTypeParsingFromYAML verifies the IPType field parsing from YAML
+// for the cloud-sql-mysql source, mimicking the structure of tests in cloudsql_mysql_test.go.
+func TestCloudSQLMySQL_IPTypeParsingFromYAML(t *testing.T) {
+	tcs := []struct {
+		desc string
+		in   string
+		want server.SourceConfigs
+	}{
+		{
+			desc: "IPType Defaulting to Public",
+			in: `
+			sources:
+				my-mysql-instance:
+					kind: cloud-sql-mysql
+					project: my-project
+					region: my-region
+					instance: my-instance
+					database: my_db
+					user: my_user
+					password: my_pass
+			`,
+			want: server.SourceConfigs{
+				"my-mysql-instance": cloudsqlmysql.Config{
+					Name:     "my-mysql-instance",
+					Kind:     cloudsqlmysql.SourceKind,
+					Project:  "my-project",
+					Region:   "my-region",
+					Instance: "my-instance",
+					IPType:   "public", // Default value
+					Database: "my_db",
+					User:     "my_user",
+					Password: "my_pass",
+				},
+			},
+		},
+		{
+			desc: "IPType Explicit Public",
+			in: `
+			sources:
+				my-mysql-instance:
+					kind: cloud-sql-mysql
+					project: my-project
+					region: my-region
+					instance: my-instance
+					ipType: Public
+					database: my_db
+					user: my_user
+					password: my_pass
+			`,
+			want: server.SourceConfigs{
+				"my-mysql-instance": cloudsqlmysql.Config{
+					Name:     "my-mysql-instance",
+					Kind:     cloudsqlmysql.SourceKind,
+					Project:  "my-project",
+					Region:   "my-region",
+					Instance: "my-instance",
+					IPType:   "public",
+					Database: "my_db",
+					User:     "my_user",
+					Password: "my_pass",
+				},
+			},
+		},
+		{
+			desc: "IPType Explicit Private",
+			in: `
+			sources:
+				my-mysql-instance:
+					kind: cloud-sql-mysql
+					project: my-project
+					region: my-region
+					instance: my-instance
+					ipType: private 
+					database: my_db
+					user: my_user
+					password: my_pass
+			`,
+			want: server.SourceConfigs{
+				"my-mysql-instance": cloudsqlmysql.Config{
+					Name:     "my-mysql-instance",
+					Kind:     cloudsqlmysql.SourceKind,
+					Project:  "my-project",
+					Region:   "my-region",
+					Instance: "my-instance",
+					IPType:   "private",
+					Database: "my_db",
+					User:     "my_user",
+					Password: "my_pass",
+				},
+			},
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			got := struct {
+				Sources server.SourceConfigs `yaml:"sources"`
+			}{}
+			// Parse contents
+			err := yaml.Unmarshal(testutils.FormatYaml(tc.in), &got)
+			if err != nil {
+				t.Fatalf("unable to unmarshal: %s", err)
+			}
+			if !cmp.Equal(tc.want, got.Sources) {
+				t.Fatalf("incorrect parse: diff (-want +got):\n%s", cmp.Diff(tc.want, got.Sources))
+			}
+		})
+	}
+}