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Gulliver

Gulliver

by laaielichter
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

gulliver_drift

Idempotent

Detect schema drift by comparing current tables and columns with the last snapshot, flagging added, removed, and retyped fields plus affected models; save a new baseline after review.

Instructions

Schema drift: compare the connection's tables and columns with the last snapshot (added, removed and retyped columns and tables). The first call saves a snapshot file in the local .gulliver folder; later calls compare against it, and save=true replaces it with the current schema. Only reads catalog metadata, never data. With models it also lists the models that removed or retyped columns break. Use it to catch upstream changes; use gulliver_impact to plan your own change, gulliver_diff to compare rows.

Input Schema

NameRequiredDescriptionDefault
saveNoAfter reviewing the drift, accept the current schema as the new baseline. Leave false to keep reporting the same changes.
manifestNoPath to a dbt target/manifest.json (alternative to models_dir).
connectionNoConnection name as listed by gulliver_status (from gulliver.toml or GULLIVER_DSN). Omit for the default connection.
models_dirNoFolder with SQL models (*.sql, dbt-style refs allowed). Use an absolute path.

Output Schema

NameRequiredDescriptionDefault
statusYes
next_stepYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv0.3.1
    • changedInput schema / properties / connection / description
      Previous value: -"Connection name from gulliver_status. Omit for the default."New value: +"Connection name as listed by gulliver_status (from gulliver.toml or GULLIVER_DSN). Omit for the default connection."
    • changedInput schema / properties / save / description
      Previous value: -"Accept the current schema as the new snapshot."New value: +"After reviewing the drift, accept the current schema as the new baseline. Leave false to keep reporting the same changes."
  2. Changed3 schema fields changedv0.1.1
    • addedOutput schema / properties
      Added value: +{
+  "next_step": {
+    "type": "string"
+  },
+  "status": {
+    "enum": [
+      "ok",
+      "warn",
+      "block",
+      "needs_rehearsal",
+      "needs_approval",
+      "skipped",
+      "fail",
+      "error"
+    ],
+    "type": "string"
+  }
+}
    • addedOutput schema / required
      Added value: +[
+  "status",
+  "next_step"
+]
    • changedOutput schema / title
      Previous value: -"gulliver_driftDictOutput"New value: +"GulliverResult"
  3. First observedv0.1.0

TDQS

A4.6/5.0
Behavior4/5

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

Adds substantial context beyond the annotations: the first call writes a snapshot file into the local .gulliver folder, later calls diff against it, and save=true replaces the baseline. It also resolves the otherwise confusing readOnlyHint=false by stating 'Only reads catalog metadata, never data' — the only writes are local snapshot files. Return/pagination behavior is not described, but an output schema exists to cover that.

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?

Five tight sentences, front-loaded with the operation and only then the stateful caveats, then alternatives. Minor redundancy where 'tables and columns' is restated in parentheses, but nothing else is wasted.

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 stateful, side-effecting-on-local-disk tool with four optional params and an output schema, the description covers what is inspected, what is written and where, what save changes, and how to pick sibling tools. Nothing an agent needs to invoke it 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 baseline is 3, and the description earns an increment by explaining the stateful effect of save ('replaces it with the current schema' / keeping the same report) and by noting that the models/manifest path yields the list of broken models. Connection and models_dir are left to their schema text.

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?

Opens with a specific verb+resource: 'Schema drift: compare the connection's tables and columns with the last snapshot', and enumerates exactly what drift means (added, removed, retyped columns and tables). It is clearly distinguishable from gulliver_diff (row comparison) and gulliver_impact (planning your own change), which are named.

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?

States the positive use case ('Use it to catch upstream changes') and explicitly routes the agent elsewhere for the two most likely confusions: gulliver_impact for planning your own change and gulliver_diff for row comparison. A 'when-not' condition is effectively supplied by those alternative routes.

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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