mcp-postgres-guard

Execute a write

execute

Destructive

Run INSERT, UPDATE, or DELETE statements with a preview of affected rows and human approval required. Refuses UPDATE or DELETE without a WHERE clause.

Instructions

Runs a single INSERT, UPDATE or DELETE. The change is first executed in a rolled-back transaction to measure exactly how many rows it affects, then that number is shown to a human for approval. UPDATE/DELETE without a WHERE clause is always refused.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "sql": "<sql>",
      "reason": "<reason>"
    },
    "name": "execute"
  }
}

Input Schema

Name	Required	Description
`sql`	Yes	A single INSERT, UPDATE or DELETE statement
`params`	No	Values for $1, $2 … placeholders
`reason`	Yes	Why this change is needed — shown to the approver

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jul 28, 2026

TDQS

A4.4/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description adds significant behavioral context beyond annotations (readOnlyHint=false, destructiveHint=true): it explains the rolled-back transaction to measure row count, human approval step, and refusal of UPDATE/DELETE without WHERE. This fully discloses safety mechanisms.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no wasted words. The first sentence states the primary purpose, the second elaborates on behavior. Front-loaded and efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of a write tool with safety concerns, the description explains the dry-run and approval flow. No output schema exists, but the description mentions row count measurement. Not fully explicit about return format, but adequate for the intended usage.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3. The description does not add substantial meaning beyond the schema; it reinforces that 'reason' is shown to the approver, but this is already in the schema. No additional parameter guidance.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool runs a single INSERT, UPDATE, or DELETE statement, specifying the verb and resource. It distinguishes from siblings (list_tables, describe_table, query) by focusing on write operations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for when to use this tool (single write statements) and notes that UPDATE/DELETE without a WHERE clause is refused. However, it does not explicitly name alternatives or state when not to use, though siblings imply read operations.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server