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@yawlabs/postgres-mcp

by YawLabs
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TypeScript
Remote

Cancel or terminate a backend

pg_kill
Destructive

Cancel a running query or terminate a backend connection by PID to clear stuck sessions. Signals the PostgreSQL backend gracefully or forcefully, requiring proper user permissions.

Instructions

Cancel a running query (SIGINT-equivalent) or terminate a backend connection (SIGTERM-equivalent) by PID. Find the PID via pg_health active_queries or pg_inspect_locks. Requires ALLOW_WRITES=1 since this changes database session state. The role in DATABASE_URL must have permission - cancelling another user's query needs the pg_signal_backend role or superuser. Note: pg_signal_backend does NOT cover superuser-owned backends - only a superuser can signal another superuser's session. Cancel is graceful; terminate is forceful. When signaled=false, the note field surfaces postgres's NOTICE explaining why (e.g. 'not a PostgreSQL backend process' for a non-pg PID, 'must be a member of...' for permission denial) so an agent can act on the specific cause rather than guess from a three-way list.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
pidYesBackend PID to signal.
modeNo`cancel` aborts the current query; `terminate` closes the connection entirely.cancel

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
pidYesEchoed back from the request.
modeYesEchoed back, after the safer 'cancel' default is applied.
noteYesOn `signaled: false`, postgres's own NOTICE explaining why -- act on this, not on the boolean.
signaledYesWhat pg_cancel_backend / pg_terminate_backend returned.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. Changed2 schema fields changedv0.12.0
    • changedInput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "additionalProperties": false,
+  "properties": {
+    "mode": {
+      "description": "Echoed back, after the safer 'cancel' default is applied.",
+      "enum": [
+        "cancel",
+        "terminate"
+      ],
+      "type": "string"
+    },
+    "note": {
+      "description": "On `signaled: false`, postgres's own NOTICE explaining why -- act on this, not on the boolean.",
+      "type": "string"
+    },
+    "pid": {
+      "description": "Echoed back from the request.",
+      "type": "number"
+    },
+    "signaled": {
+      "description": "What pg_cancel_backend / pg_terminate_backend returned.",
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "pid",
+    "mode",
+    "signaled",
+    "note"
+  ],
+  "type": "object"
+}
  2. First observedv0.7.0

TDQS

A4.9/5.0
Behavior5/5

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

Goes well beyond the annotations: explains that cancel is graceful and terminate is forceful, that it changes database session state, and describes the signaled=false note behavior including concrete examples of cause-specific messages. Annotations already mark it destructive and non-readonly, and the description enriches rather than contradicts them.

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?

The description is information-dense without padding. Core operation is front-loaded, followed by prerequisites, permission nuances, and failure interpretation. Each sentence contributes necessary operational knowledge.

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

Completeness5/5

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

Covers prerequisites, permissions, mode differences, failure causes, and how to find inputs. An output schema exists, so return value details are not required. Nothing material is missing for an agent to select and invoke this tool correctly.

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

Parameters4/5

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 adds value by explaining the practical meaning of mode ('Cancel is graceful; terminate is forceful') and how to obtain the PID, plus the behavior of signaled=false for interpreting failures. This exceeds baseline but PID semantics remain largely defined by the schema.

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?

Description states a specific verb/resource pair: cancel a running query or terminate a backend by PID. It names the signal equivalents (SIGINT/SIGTERM), making the behavior unambiguous. It is clearly distinguished from sibling read-only tools like pg_health and pg_inspect_locks.

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

Usage Guidelines5/5

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

Provides explicit guidance on when to use the tool and prerequisites: find PID via pg_health or pg_inspect_locks, require ALLOW_WRITES=1, and need pg_signal_backend role or superuser. It also explains the permission limitation around superuser-owned backends, so an agent knows when this tool will fail.

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

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