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Supabase Read-Only MCP Server

Supabase Read-Only MCP Server

by rubenyh
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Describe Table

describe_table

Returns safe column metadata for an allowlisted schema and table, rejecting all other requests.

Instructions

Describe safe column metadata for one allowlisted schema/table; rejects all others.

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>",
      "table": "<table>"
    },
    "name": "describe_table"
  }
}

Input Schema

NameRequiredDescriptionDefault
tableYes
schemaYes

Output Schema

NameRequiredDescriptionDefault
okYes
errorNo
tableYes
schemaYes
columnsNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.1/5.0
Behavior2/5

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

With no annotations, the description must carry full behavioral disclosure. It only notes that non-allowlisted inputs are rejected, but omits details on permissions, safety guarantees, return format, or error behavior beyond rejection. 'Safe' is vague and adds little concrete behavioral context.

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?

A single, front-loaded sentence with zero waste. The key constraint is stated directly and no unnecessary words are included.

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?

For a simple two-parameter tool with an output schema already covering return values, the description covers purpose and allowlist restriction adequately. However, it lacks routing to list_allowed_tables and provides no parameter format details, leaving clear gaps for an agent to infer.

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%, so the description must compensate. It names 'schema/table' but adds no format, case-sensitivity, or distinction details beyond the allowlist constraint. This is minimal added meaning over the bare parameter names.

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?

States a specific verb (Describe) and resource (safe column metadata) with a clear scope (one allowlisted schema/table). Distinguishes from sibling tools by focusing on column metadata rather than listing tables or selecting rows, though it does not name alternatives explicitly.

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

Usage Guidelines3/5

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

The allowlist requirement ('one allowlisted schema/table; rejects all others') provides a clear usage condition, but there is no mention of how to discover allowed tables (e.g., via list_allowed_tables) or when to prefer this over other tools. Usage is implied rather than fully guided.

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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