pg_write_query
Execute a write SQL query (INSERT, UPDATE, DELETE). Returns affected row count. Pass transactionId to execute within a transaction.
This record as markdown: /tools/io-github-neverinfamous-postgres-mcp/pg-write-query.md
What pg_write_query does on PostgreSQL MCP Server
AI agents use pg_write_query to create or update resources in PostgreSQL MCP Server, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your PostgreSQL MCP Server environment.
Why pg_write_query is rated Medium
This tool creates or modifies data reversibly through INSERT, UPDATE, and DELETE operations. While DELETE can remove data, the tool's design permits transaction control (via transactionId parameter), suggesting reversibility through rollback is intended. It does not permanently destroy data like a DROP or TRUNCATE would.
From the tool's definition Tool description explicitly states 'Execute a write SQL query (INSERT, UPDATE, DELETE)'. The name 'pg_write_query' and description directly indicate data modification capabilities.
Attacks that exploit this kind of access
The rule that runs pg_write_query safely
PolicyLayer is an MCP gateway: it sits between your AI agents and PostgreSQL MCP Server, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For pg_write_query, this is the rule to start with:
pg_write_query stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect PostgreSQL MCP Server, apply this rule, and every pg_write_query call is checked against it from then on.
Questions about pg_write_query
Execute a write SQL query (INSERT, UPDATE, DELETE). Returns affected row count. Pass transactionId to execute within a transaction. It is categorised as a Write tool in the PostgreSQL MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the PostgreSQL MCP Server MCP server in PolicyLayer and add a rule for pg_write_query: 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 PostgreSQL MCP Server. Nothing to install.
pg_write_query is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the pg_write_query 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 pg_write_query. 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.
pg_write_query is provided by the PostgreSQL MCP Server MCP server (@neverinfamous/postgres-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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