pg_jsonb_merge

Merge two JSONB objects. deep=true (default) recursively merges. mergeArrays=true concatenates arrays.

SERVERPostgreSQL MCP Server SOURCE@neverinfamous/postgres-mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-neverinfamous-postgres-mcp/pg-jsonb-merge.md

WHAT IT DOES

What pg_jsonb_merge does on PostgreSQL MCP Server

AI agents use pg_jsonb_merge 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.

RISK

Why pg_jsonb_merge is rated Medium

pg_jsonb_merge modifies JSONB column data by merging/concatenating values. This is a reversible write operation (the original data could theoretically be reconstructed or the merge could be undone via a transaction), distinguishing it from destructive operations.

From the tool's definition Tool performs 'Merge' operation on JSONB objects with options to recursively merge and concatenate arrays, modifying data structure in the database.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs pg_jsonb_merge 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_jsonb_merge, this is the rule to start with:

pg_jsonb_merge Rate-limited

pg_jsonb_merge 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "pg_jsonb_merge": {
      "limits": [
        {
          "counter": "pg_jsonb_merge_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect PostgreSQL MCP Server, apply this rule, and every pg_jsonb_merge call is checked against it from then on.

FAQ

Questions about pg_jsonb_merge

What does the pg_jsonb_merge tool do? +

Merge two JSONB objects. deep=true (default) recursively merges. mergeArrays=true concatenates arrays. 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.

How do I enforce a policy on pg_jsonb_merge? +

Register the PostgreSQL MCP Server MCP server in PolicyLayer and add a rule for pg_jsonb_merge: 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.

What risk level is pg_jsonb_merge? +

pg_jsonb_merge is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit pg_jsonb_merge? +

Yes. Add a rate_limit block to the pg_jsonb_merge 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.

How do I block pg_jsonb_merge completely? +

Set action: deny in the PolicyLayer policy for pg_jsonb_merge. 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.

What MCP server provides pg_jsonb_merge? +

pg_jsonb_merge 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.

KEEP EXPLORING

What pg_jsonb_merge does on PostgreSQL MCP Server

Why pg_jsonb_merge is rated Medium

The rule that runs pg_jsonb_merge safely

Questions about pg_jsonb_merge

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