SafeSelect Read-only database MCP servers: choosing the right boundary
Reviewed: 2026-08-28. Written by the SafeSelect maintainers. This is a documentation-based comparison, not an independent security audit or a benchmark. SafeSelect's current release is v0.7.6; competitor documentation is a dated snapshot of the linked pages, not a guarantee about every version.
An MCP server can make a database easier to use without making every operation appropriate for an agent. Start with what the agent needs to do, where policy is enforced, and which credentials and other tools it can access.
At a glance
| Project | Documented contract and boundary | Deployment and scope | Choose it when |
|---|---|---|---|
| SafeSelect MCP | Fixed database read tools, Rust validation and a second sidecar check; project policy and row/byte/time limits. Security violations terminate the process. | Local MCP stdio; PostgreSQL and MongoDB. Java 17+ required. | Coding agents need direct but constrained database inspection across these two backends, with connection import and inspectable security evidence. |
| DBHub | Configurable tools; readonly = true combines a keyword classifier with engine read-only enforcement where documented. Limits and custom SQL tools are configurable. |
Multiple SQL engines, including PostgreSQL, MySQL, MariaDB, SQL Server and SQLite; stdio/HTTP options. | Multiple SQL engines, a small default tool surface, custom operations or a workbench matter more than a fixed read-only product contract. Sources: introduction and SQL tool. |
| MongoDB MCP Server | --readOnly restricts tools to read, connect and metadata operations. The documented default permits writes. MongoDB recommends a dedicated read-only database user too. |
Official MongoDB integration. This row concerns its local server, not every hosted or Atlas configuration. | An official MongoDB-specific integration is the priority and you can manage the read-only setting and database permissions. Source: security guidance. |
| Postgres MCP Pro | Configurable access: restricted mode uses read-only transactions and an execution-time constraint; unrestricted mode supports writes. | PostgreSQL; local stdio or shared SSE deployment. Performance-analysis tooling is a major part of the offering. | PostgreSQL health analysis, index tuning and DBA workflows are central. Source: access modes and tools. |
| SchemaBrain | Compiles queries from controlled definitions rather than accepting raw agent SQL; documents PII-aware refusal and tamper-evident auditing. | PostgreSQL source support in its documented beta; a semantic layer rather than a general raw-SQL tool. | Governed entities, joins and metrics are more useful than free-form database inspection. Source: architecture and current support. |
DBHub's introduction describes its supported engines and deployment options. Its read-only documentation explicitly discusses engine-specific limitations and privileged functions. It should not be described as merely a naive SELECT-prefix wrapper.
What SafeSelect does—and does not—claim
SafeSelect exposes no database mutation, migration or administration tools. It applies policy to SQL and MongoDB operations before execution, rather than asking the agent to remember a rule. The same product provides DBeaver, Compose and Compass imports, agent installation, scoped discovery, query limits and audit metadata. See the README, security model and Security Proof.
The boundary applies only to requests through SafeSelect. A shell, another MCP server, exposed credentials or a compromised host can provide a separate route to the database. Readable data can still be sensitive. Read-only queries can still cost resources. Native permissions and deliberate data selection remain necessary.
Fail-closed is a tradeoff: terminating on a security violation reduces continued use of that session, but the operator must correct the cause before restarting. It is not evidence that a competitor returning an error is inherently unsafe.
Evidence, not checkmark theatre
SafeSelect publishes a threat model and claim-to-test mapping and a security suite execution contract. Real-database tests must use explicitly disposable fixtures. A test definition is not a test run, and a passing suite is not proof against every future bypass.
The competitor rows describe their authors' documentation. We did not execute their test suites or establish that a feature absent from these pages is absent from the product. This comparison makes no universal "most secure" ranking.
For your deployment, verify:
- Which tools are exposed in the actual installed version and configuration?
- Can a configuration change enable writes? Who controls that configuration?
- Is enforcement in tool selection, query validation, the driver/database—or several layers? What happens if one layer fails?
- Which data, functions and resources can the effective database role access?
- Are secrets, query logs and results handled according to your requirements?
- Can the agent bypass this connection through a different tool?
SafeSelect versus a read-only database role
These are complementary controls, not mutually exclusive products. A database role is the native authority on permissions. SafeSelect adds an agent-facing tool contract, project policy, bounded results, connection setup and auditing. Use both; do not broaden a production account just to demonstrate the proxy.
SafeSelect versus handing the agent a shell
A shell with database credentials provides a broader execution surface than a fixed MCP tool set. SafeSelect can constrain its own connection, but cannot remove permissions from a shell you also give the agent. Keep configuration and secrets under operator control, and review the agent's entire tool set.
Start with your use case
- For PostgreSQL + MongoDB inspection by coding agents, try SafeSelect's DBeaver-to-Codex guide.
- For broader SQL connectivity, evaluate DBHub's documented engines and deployment model.
- For MongoDB platform integration, evaluate the official server.
- For PostgreSQL performance workflows, evaluate Postgres MCP Pro.
- For curated semantic analytics and PII policy, evaluate SchemaBrain.
Found an outdated statement? Open an issue with the relevant version and a primary source. Security reports belong in the private disclosure process.