AI agents call list_user_defined_types to retrieve information from Mssql without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
schema | string | — | Schema name (default: dbo) |
connectionName | string | — | Named connection to use (e.g., 'production', 'staging') |
connectionString | string | — | SQL Server connection string (uses default if not provided) |
Parameters from the server's own tool schema.
This tool retrieves schema metadata about user-defined types without creating, modifying, or deleting any data or objects. It is a passive query operation. Severity is medium rather than low because it exposes database schema structure that could inform privilege escalation or attack surface mapping by a compromised agent.
From the tool's definition Tool name 'list_user_defined_types' and description 'List all user-defined data types and their definitions' indicate data retrieval with no modification. Uses 'list' and 'definitions' which are read operations.
Risk signalsBulk/mass operation — affects multiple targets
Attacks that exploit this kind of access
List all user-defined data types and their definitions. It is categorised as a Read tool in the Mssql MCP Server, which means it retrieves data without modifying state.
list_user_defined_types accepts 3 parameters: schema, connectionName, connectionString. The full parameter table on this page comes from the server's own tool schema.
Register the Mssql MCP server in PolicyLayer and add a rule for list_user_defined_types: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Mssql. Nothing to install.
list_user_defined_types is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_user_defined_types rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for list_user_defined_types. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
list_user_defined_types is provided by the Mssql MCP server (mssql-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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