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MCPg - Production-grade PostgreSQL MCP Server

MCPg - Production-grade PostgreSQL MCP Server

by devopam
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Generate FK cascade graph

generate_fk_cascade_graph
Read-only

Build a Mermaid graph LR of PostgreSQL foreign-key cascade chains, with edges from referencing to referenced tables labeled by DELETE/UPDATE actions. Use include_all to show full FK topology.

Instructions

Build a Mermaid graph LR of foreign-key cascade chains in a schema. Each edge runs from the referencing table to the referenced table, labelled with the cascade action(s) on DELETE / UPDATE. By default only FKs with at least one CASCADE / SET NULL / SET DEFAULT action are included — those are the ones that produce a write blast radius. Pass include_all=true to include NO ACTION / RESTRICT FKs too (full FK topology view). Cross-schema FK targets are rendered as separate nodes prefixed with their schema. Returns the Mermaid graph LR diagram as a string.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "schema": "<schema>"
    },
    "name": "generate_fk_cascade_graph"
  }
}

Input Schema

NameRequiredDescriptionDefault
schemaYes
databaseNoOptional: a database id from list_databases, to target a configured secondary (read-only) database; omit for the primary. Database names that are not configured ids are rejected.
include_allNo

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.8.4
    • changedInput schema / properties / database / description
      Previous value: -"Optional: target a configured secondary (read-only) database by name; omit for the primary. Call list_databases to see the configured ids."New value: +"Optional: a database id from list_databases, to target a configured secondary (read-only) database; omit for the primary. Database names that are not configured ids are rejected."
  2. First observedv0.6.8

TDQS

A4.7/5.0
Behavior5/5

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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the default filtering rule and its rationale, the direction and label semantics of each edge, how cross-schema targets are rendered as prefixed nodes, and the return type. That is substantial behavioural context an agent could not infer from annotations.

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?

Front-loaded with the artifact produced, then default behaviour, then the opt-in flag, then rendering and return details. Every sentence adds information with no repetition of the schema or annotations.

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 three-parameter generator with an output schema, the description covers purpose, default vs. full mode, edge semantics and output type. 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 only 33%, but the description fully explains include_all (its default false, what it adds, when to use it) and the schema field itself documents database. The required 'schema' parameter's meaning is only implied by context, leaving one small gap.

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?

States a specific verb ('Build') and a precise resource ('Mermaid graph LR of foreign-key cascade chains in a schema'), and the edge direction and labelling are defined. It is clearly distinct from siblings like generate_schema_diagram and list_foreign_keys, which produce other artifacts.

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?

The description explicitly gives the default behaviour (only CASCADE/SET NULL/SET DEFAULT FKs, chosen because they carry write blast radius) and the branch to opt into full topology via include_all=true. It does not name sibling tools to prefer over this one, so it stops short of a 5.

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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