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describe_schema

Read-onlyIdempotent

Introspect the full database structure for a connection: every table, column, type, primary key, foreign key, and index — the map to build queries against an unfamiliar database. Use analyze_table or data_profile instead when you need column VALUES (stats, nulls, PII) rather than structure. Read-only against your database. Results are cached 1 hour per connection; pass refresh=true to force a live re-introspection and bypass that cache, e.g. right after altering the schema. Does not consume daily quota. Returns tables with their columns, types, keys, and indexes.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
refreshNoForce live introspection, bypassing cache
connectionNoTarget connection name from this tenant's inventory. Call `list_connections` to see every name + dialect, then match semantically to the user's intent (e.g. 'analytics' → a connection named `*-analytics-*`; 'prod' → a connection with `prod-` prefix). If the user didn't specify, use the tenant's default (first added). Do not invent names — resolve from `list_connections` output.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataNo
metaNo
displayNo
summaryNo
insightsNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / properties / data / anyOf
      Previous value: -[
      -  {
      -    "items": {
      -      "additionalProperties": true,
      -      "properties": {
      -        "columns": {
      -          "type": [
      -            "number",
      -            "string"
      -          ]
      -        },
      -        "details": {
      -          "items": {
      -            "additionalProperties": true,
      -            "properties": {
      -              "defaultValue": {
      -                "type": [
      -                  "string",
      -                  "null"
      -                ]
      -              },
      -              "isPrimaryKey": {
      -                "type": "boolean"
      -              },
      -              "name": {
      -                "type": "string"
      -              },
      -              "nullable": {
      -                "type": "boolean"
      -              },
      -              "type": {
      -                "type": "string"
      -              }
      -            },
      -            "required": [
      -              "name",
      -              "type"
      -            ],
      -            "type": "object"
      -          },
      -          "type": "array"
      -        },
      -        "name": {
      -          "type": "string"
      -        },
      -        "primaryKeys": {
      -          "items": {
      -            "type": "string"
      -          },
      -          "type": "array"
      -        }
      -      },
      -      "required": [
      -        "name"
      -      ],
      -      "type": "object"
      -    },
      -    "type": "array"
      -  },
      -  {
      -    "additionalProperties": true,
      -    "properties": {
      -      "code": {
      -        "type": "string"
      -      },
      -      "details": {
      -        "additionalProperties": {},
      -        "type": "object"
      -      },
      -      "error": {
      -        "type": "string"
      -      },
      -      "internal_code": {
      -        "type": "string"
      -      },
      -      "message": {
      -        "type": "string"
      -      },
      -      "retry_after_s": {
      -        "type": "number"
      -      }
      -    },
      -    "type": "object"
      -  }
      -]New value: +[
      +  {
      +    "items": {
      +      "additionalProperties": true,
      +      "properties": {
      +        "columns": {
      +          "type": [
      +            "number",
      +            "string"
      +          ]
      +        },
      +        "details": {
      +          "items": {
      +            "additionalProperties": true,
      +            "properties": {
      +              "defaultValue": {
      +                "type": [
      +                  "string",
      +                  "null"
      +                ]
      +              },
      +              "isPrimaryKey": {
      +                "type": "boolean"
      +              },
      +              "name": {
      +                "type": "string"
      +              },
      +              "nullable": {
      +                "type": "boolean"
      +              },
      +              "type": {
      +                "type": "string"
      +              }
      +            },
      +            "required": [
      +              "name",
      +              "type"
      +            ],
      +            "type": "object"
      +          },
      +          "type": "array"
      +        },
      +        "name": {
      +          "type": "string"
      +        },
      +        "primaryKeys": {
      +          "items": {
      +            "type": "string"
      +          },
      +          "type": "array"
      +        }
      +      },
      +      "required": [
      +        "name"
      +      ],
      +      "type": "object"
      +    },
      +    "type": "array"
      +  },
      +  {
      +    "additionalProperties": true,
      +    "properties": {
      +      "code": {
      +        "type": "string"
      +      },
      +      "details": {
      +        "additionalProperties": {},
      +        "type": "object"
      +      },
      +      "error": {
      +        "type": "string"
      +      },
      +      "internal_code": {
      +        "type": "string"
      +      },
      +      "message": {
      +        "type": "string"
      +      },
      +      "retry_after_s": {
      +        "type": "number"
      +      }
      +    },
      +    "required": [
      +      "error"
      +    ],
      +    "type": "object"
      +  }
      +]
  2. Changed1 schema field changed
    • addedInput schema / properties / connection / maxLength
      Added value: +256
  3. Changed2 schema fields changed
    • addedOutput schema / properties / display / properties / map
      Added value: +{
      +  "additionalProperties": true,
      +  "properties": {
      +    "label": {
      +      "type": "string"
      +    },
      +    "lat": {
      +      "type": "string"
      +    },
      +    "lon": {
      +      "type": "string"
      +    },
      +    "title": {
      +      "type": "string"
      +    }
      +  },
      +  "type": "object"
      +}
    • changedOutput schema / properties / display / properties / type / anyOf
      Previous value: -[
      -  {
      -    "enum": [
      -      "table",
      -      "chart",
      -      "metric",
      -      "code",
      -      "text",
      -      "list"
      -    ],
      -    "type": "string"
      -  },
      -  {
      -    "type": "string"
      -  }
      -]New value: +[
      +  {
      +    "enum": [
      +      "table",
      +      "chart",
      +      "metric",
      +      "code",
      +      "text",
      +      "list",
      +      "map"
      +    ],
      +    "type": "string"
      +  },
      +  {
      +    "type": "string"
      +  }
      +]
  4. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "$schema": "http://json-schema.org/draft-07/schema#",
      +  "additionalProperties": true,
      +  "properties": {
      +    "data": {
      +      "anyOf": [
      +        {
      +          "items": {
      +            "additionalProperties": true,
      +            "properties": {
      +              "columns": {
      +                "type": [
      +                  "number",
      +                  "string"
      +                ]
      +              },
      +              "details": {
      +                "items": {
      +                  "additionalProperties": true,
      +                  "properties": {
      +                    "defaultValue": {
      +                      "type": [
      +                        "string",
      +                        "null"
      +                      ]
      +                    },
      +                    "isPrimaryKey": {
      +                      "type": "boolean"
      +                    },
      +                    "name": {
      +                      "type": "string"
      +                    },
      +                    "nullable": {
      +                      "type": "boolean"
      +                    },
      +                    "type": {
      +                      "type": "string"
      +                    }
      +                  },
      +                  "required": [
      +                    "name",
      +                    "type"
      +                  ],
      +                  "type": "object"
      +                },
      +                "type": "array"
      +              },
      +              "name": {
      +                "type": "string"
      +              },
      +              "primaryKeys": {
      +                "items": {
      +                  "type": "string"
      +                },
      +                "type": "array"
      +              }
      +            },
      +            "required": [
      +              "name"
      +            ],
      +            "type": "object"
      +          },
      +          "type": "array"
      +        },
      +        {
      +          "additionalProperties": true,
      +          "properties": {
      +            "code": {
      +              "type": "string"
      +            },
      +            "details": {
      +              "additionalProperties": {},
      +              "type": "object"
      +            },
      +            "error": {
      +              "type": "string"
      +            },
      +            "internal_code": {
      +              "type": "string"
      +            },
      +            "message": {
      +              "type": "string"
      +            },
      +            "retry_after_s": {
      +              "type": "number"
      +            }
      +          },
      +          "type": "object"
      +        }
      +      ]
      +    },
      +    "display": {
      +      "additionalProperties": true,
      +      "properties": {
      +        "chart": {
      +          "additionalProperties": true,
      +          "properties": {
      +            "chartType": {
      +              "type": "string"
      +            },
      +            "color": {
      +              "type": "string"
      +            },
      +            "title": {
      +              "type": "string"
      +            },
      +            "x": {
      +              "type": "string"
      +            },
      +            "xLabel": {
      +              "type": "string"
      +            },
      +            "y": {
      +              "anyOf": [
      +                {
      +                  "type": "string"
      +                },
      +                {
      +                  "items": {
      +                    "type": "string"
      +                  },
      +                  "type": "array"
      +                }
      +              ]
      +            },
      +            "yLabel": {
      +              "type": "string"
      +            }
      +          },
      +          "type": "object"
      +        },
      +        "code": {
      +          "additionalProperties": true,
      +          "properties": {
      +            "executable": {
      +              "type": "boolean"
      +            },
      +            "language": {
      +              "anyOf": [
      +                {
      +                  "enum": [
      +                    "sql",
      +                    "json",
      +                    "bash",
      +                    "typescript"
      +                  ],
      +                  "type": "string"
      +                },
      +                {
      +                  "type": "string"
      +                }
      +              ]
      +            },
      +            "title": {
      +              "type": "string"
      +            }
      +          },
      +          "type": "object"
      +        },
      +        "metric": {
      +          "additionalProperties": true,
      +          "properties": {
      +            "label": {
      +              "type": "string"
      +            },
      +            "status": {
      +              "anyOf": [
      +                {
      +                  "enum": [
      +                    "good",
      +                    "warning",
      +                    "critical"
      +                  ],
      +                  "type": "string"
      +                },
      +                {
      +                  "type": "string"
      +                }
      +              ]
      +            },
      +            "trend": {
      +              "anyOf": [
      +                {
      +                  "enum": [
      +                    "up",
      +                    "down",
      +                    "neutral"
      +                  ],
      +                  "type": "string"
      +                },
      +                {
      +                  "type": "string"
      +                }
      +              ]
      +            },
      +            "trendValue": {
      +              "type": "string"
      +            },
      +            "unit": {
      +              "type": "string"
      +            },
      +            "value": {
      +              "type": [
      +                "string",
      +                "number"
      +              ]
      +            }
      +          },
      +          "type": "object"
      +        },
      +        "type": {
      +          "anyOf": [
      +            {
      +              "enum": [
      +                "table",
      +                "chart",
      +                "metric",
      +                "code",
      +                "text",
      +                "list"
      +              ],
      +              "type": "string"
      +            },
      +            {
      +              "type": "string"
      +            }
      +          ]
      +        }
      +      },
      +      "type": "object"
      +    },
      +    "insights": {
      +      "items": {
      +        "additionalProperties": true,
      +        "properties": {
      +          "column": {
      +            "type": "string"
      +          },
      +          "message": {
      +            "type": "string"
      +          },
      +          "severity": {
      +            "anyOf": [
      +              {
      +                "enum": [
      +                  "info",
      +                  "warning",
      +                  "critical"
      +                ],
      +                "type": "string"
      +              },
      +              {
      +                "type": "string"
      +              }
      +            ]
      +          },
      +          "value": {}
      +        },
      +        "required": [
      +          "severity",
      +          "message"
      +        ],
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "meta": {
      +      "additionalProperties": true,
      +      "properties": {
      +        "cacheHit": {
      +          "type": "boolean"
      +        },
      +        "connection": {
      +          "type": "string"
      +        },
      +        "dialect": {
      +          "anyOf": [
      +            {
      +              "enum": [
      +                "postgres",
      +                "mysql",
      +                "mssql"
      +              ],
      +              "type": "string"
      +            },
      +            {
      +              "type": "string"
      +            }
      +          ]
      +        },
      +        "executionTimeMs": {
      +          "$ref": "#/properties/data/anyOf/0/items/properties/columns"
      +        },
      +        "plan": {},
      +        "rowCount": {
      +          "$ref": "#/properties/data/anyOf/0/items/properties/columns"
      +        },
      +        "tool": {
      +          "type": "string"
      +        },
      +        "truncated": {
      +          "type": "boolean"
      +        }
      +      },
      +      "type": "object"
      +    },
      +    "summary": {
      +      "type": "string"
      +    }
      +  },
      +  "type": "object"
      +}
  5. First observed

TDQS

A4.8/5.0
Behavior5/5

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint. The description adds important non-obvious behavior beyond annotations: 1-hour per-connection caching, the refresh=true escape hatch, and the fact that it does not consume daily quota. No contradiction with annotations.

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

Conciseness4/5

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

The description is moderately sized but every sentence provides distinct value: purpose, alternatives, read-only safety, caching behavior, quota note, and return contents. It is front-loaded with the core purpose. Slightly dense, but not wasteful.

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?

The tool takes only optional parameters, has an output schema, and carries strong annotations. The description covers usage context, alternatives, safety, cache behavior, and output contents. Nothing an agent needs to decide whether to call it and how to do so correctly is missing.

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 the schema carries most parameter documentation. The description adds contextual meaning to refresh by explaining the 1-hour cache it bypasses, which goes beyond the schema's 'Force live introspection, bypassing cache'. The connection parameter is already richly documented in 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?

Uses a specific verb ('Introspect') with a clear resource ('full database structure for a connection') and enumerates the returned content: tables, columns, types, keys, and indexes. It also differentiates itself from sibling tools analyze_table and data_profile, making its purpose unambiguous.

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?

Explicitly states when to use this tool versus alternatives: 'Use analyze_table or data_profile instead when you need column VALUES...' It also gives concrete operational guidance about caching and refresh behavior, so an agent knows exactly when to invoke it.

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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