YDB MCP

Official

Overview Schema Source Related Servers Discussions Admin

ydb_query

Run read-only SQL queries on YDB databases to retrieve data without altering the database. Ideal for safe, non-destructive data exploration.

Instructions

Run a read-only SQL query against YDB database

Input Schema

TableJSON Schema

Name	Required	Description	Default
`sql`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedv0.1.4May 1, 2026

removedInput schema / properties / params

Removed value: -{
-  "anyOf": [
-    {
-      "additionalProperties": true,
-      "type": "object"
-    },
-    {
-      "type": "null"
-    }
-  ],
-  "default": null,
-  "title": "Params"
-}

changedInput schema / title

Previous value: -"queryArguments"New value: +"ydb_queryArguments"

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$defs": {
+    "Annotations": {
+      "additionalProperties": true,
+      "properties": {
+        "audience": {
+          "anyOf": [
+            {
+              "items": {
+                "enum": [
+                  "user",
+                  "assistant"
+                ],
+                "type": "string"
+              },
+              "type": "array"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Audience"
+        },
+        "priority": {
+          "anyOf": [
+            {
+              "maximum": 1,
+              "minimum": 0,
+              "type": "number"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Priority"
+        }
+      },
+      "title": "Annotations",
+      "type": "object"
+    },
+    "TextContent": {
+      "additionalProperties": true,
+      "description": "Text content for a message.",
+      "properties": {
+        "_meta": {
+          "anyOf": [
+            {
+              "additionalProperties": true,
+              "type": "object"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Meta"
+        },
+        "annotations": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/Annotations"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null
+        },
+        "text": {
+          "title": "Text",
+          "type": "string"
+        },
+        "type": {
+          "const": "text",
+          "title": "Type",
+          "type": "string"
+        }
+      },
+      "required": [
+        "type",
+        "text"
+      ],
+      "title": "TextContent",
+      "type": "object"
+    }
+  },
+  "properties": {
+    "result": {
+      "items": {
+        "$ref": "#/$defs/TextContent"
+      },
+      "title": "Result",
+      "type": "array"
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "title": "ydb_queryOutput",
+  "type": "object"
+}

First observedAug 14, 2025

TDQS

B3.1/5.0

Behavior3/5

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

The description discloses that the operation is 'read-only', which is a useful safety-related behavioral trait, especially since no annotations are provided. However, it does not mention return behavior, error cases, or limitations, so the description only partially carries the behavioral transparency burden.

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 a single focused sentence with no filler. It front-loads the action and resource, and every word contributes to meaning.

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

Completeness3/5

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

The tool is simple, has an output schema to cover return values, and one obvious parameter, so the description is nearly adequate. However, it lacks any usage guidance relative to the sibling tools, leaving an important gap for correct tool selection.

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

Parameters2/5

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

Schema description coverage is 0%, and the description does not explain the 'sql' parameter beyond implying it contains the query text. With only one required parameter, the gap is small, but the description still fails to explicitly document what the parameter should contain.

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

Purpose4/5

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

The description names a specific verb ('Run') and resource ('SQL query against YDB database'), clearly stating the tool's core purpose. However, it does not explicitly distinguish this from the sibling ydb_query_with_params, so sibling differentiation is absent.

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

Usage Guidelines2/5

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

No guidance is given about when to use this tool instead of ydb_query_with_params, ydb_explain_query, or the other siblings. The description simply states what it does, leaving the agent to infer selection criteria from the tool name alone.

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

Deploy Server