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@yawlabs/postgres-mcp

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TypeScript
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List tables in a schema

pg_list_tables
Read-onlyIdempotent

List PostgreSQL tables in a schema, optionally including views, with type and estimated row count to quickly assess table sizes and structure.

Instructions

List tables (and optionally views) in a schema. Returns name, type (table/view/materialized view/foreign), and estimated row count (from reltuples; null = no ANALYZE yet on PG 14+; 0 may mean empty or unanalyzed on PG <= 13). Paginate via limit/offset on very large schemas.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
limitNoMax rows to return (default 500, max 10000).
offsetNoRows to skip for pagination (default 0).
schemaNoSchema name (defaults to 'public').public
includeViewsNoIf true, include views and materialized views.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
rowsYes

Schema Changelog

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

  1. Changed2 schema fields changedv0.12.1
    • removedOutput schema / properties / rows / items / properties / estimated_rows / anyOf
      Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]
    • addedOutput schema / properties / rows / items / properties / estimated_rows / type
      Added value: +[
+  "number",
+  "null"
+]
  2. 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": {
+    "rows": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "estimated_rows": {
+            "anyOf": [
+              {
+                "type": "number"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Estimate from reltuples. Null = never ANALYZEd (PG14+); on PG<=13 a never-analyzed table reports 0 instead, indistinguishable from empty."
+          },
+          "name": {
+            "type": "string"
+          },
+          "type": {
+            "description": "table | view | materialized_view | foreign_table | partitioned_table, or the raw relkind.",
+            "type": "string"
+          }
+        },
+        "required": [
+          "name",
+          "type",
+          "estimated_rows"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "rows"
+  ],
+  "type": "object"
+}
  3. First observedv0.7.0

TDQS

A4.5/5.0
Behavior5/5

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

Annotations already establish read-only/idempotent/non-destructive behavior. The description adds valuable semantic caveats about row-count estimation: null vs 0 and PG version differences, which the annotations cannot express.

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?

Three sentences, all information-dense; the core action and optional flag lead, and caveats are packed without redundancy. Every sentence earns its place.

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?

For a read-only list operation, annotations plus a complete schema plus an output schema already cover safety and return structure. The description adds the version-specific row-count interpretation and pagination, so nothing an agent needs to call it correctly is missing.

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 descriptions cover 100% of parameters, each with defaults and constraints, so the baseline is 3. The description's pagination mention mostly mirrors limit/offset schema docs and adds no new parameter-specific meaning.

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 opening clause 'List tables (and optionally views) in a schema' names a specific verb, a concrete resource, and an optional extension. This clearly distinguishes it from sibling tools like pg_list_views and pg_describe_table.

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?

It gives clear context for when to use: listing tables in a schema, with includeViews for views, and explicit pagination advice for very large schemas. It does not name sibling alternatives or state when not to use this tool, but the context is strong enough for an agent to decide.

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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