pii-safe-db-mcp

Describe table

describe_table

Read-only

Show a table’s columns, data types, and PII status so you can see which fields will be masked or blocked before querying.

Instructions

Show the columns of a table, their types, and whether each column is classified as PII (and will be masked) or blocked.

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

Input Schema

Name	Required	Description	Default
`table`	Yes	Table name, optionally schema-qualified (schema.table).

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Nov 7, 2026

TDQS

A3.6/5.0

Behavior3/5

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

readOnlyHint=true already declares the safety profile, so the description's job is lighter. It does add genuinely useful behavioral context — that the output reports whether a column is PII-masked or blocked — but says nothing about lookup failure behavior for a nonexistent table or how an unauthorized/blocked column is represented in the result, which matters given there is no output schema.

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?

One front-loaded sentence that lists the returned fields in a natural reading order and contains no filler or redundancy. Nothing could be removed without losing information.

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

Completeness4/5

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

For a one-parameter, read-only introspection tool with no output schema, the description covers the key question an agent has — what comes back — including the PII and blocked flags. Only the failure/error semantics and the sibling boundary are left unstated.

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

Parameters3/5

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

There is a single parameter with 100% schema description coverage, and the schema already documents that it may be schema-qualified (schema.table). The description adds no meaning beyond that, so the baseline of 3 applies.

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 uses a specific verb ('Show') with a clear resource (a table's columns) and enumerates the returned attributes: column names, types, and PII/blocked classification. It is easy to tell apart from list_tables and query, but it never names those siblings or states the boundary with pii_scan, which also deals with PII classification.

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?

Usage is only implied: an agent can infer this is the introspection tool to use before writing a query or checking masking status on a single table. There is no explicit when-to-use guidance and no exclusion explaining why an agent would pick this over pii_scan or list_tables.

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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