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MCPg - Production-grade PostgreSQL MCP Server

MCPg - Production-grade PostgreSQL MCP Server

by devopam
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

List chunks

list_chunks
Read-only

List TimescaleDB hypertable chunks with their time ranges, compression status, and size; returns empty when the table is not a hypertable.

Instructions

List the chunks of a TimescaleDB hypertable with each chunk's range_start / range_end and whether it has been compressed. Empty list when the table is not a hypertable. Returns an object with available (bool) and chunks (list of {chunk_name, range_start, range_end, is_compressed, total_size_bytes}).

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": "list_chunks"
  }
}

Input Schema

NameRequiredDescriptionDefault
tableYes
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.

Output Schema

NameRequiredDescriptionDefault
chunksYes
availableYes

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

A3.6/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real behavior beyond that: the non-hypertable case yields an empty list and an `available` flag, which tells the agent how to interpret a null-looking result. It stops short of noting whether the target database must be the primary.

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?

Three short sentences, front-loaded with the action and its output, then the edge case, then the return shape. Nothing is repeated and nothing is filler.

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 simple read-only listing tool with annotations and an output schema, this is close to sufficient: the caller knows what it returns and how a non-hypertable target behaves. The remaining gap is parameter-level meaning for `schema`/`table`, which the description does not fill.

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 coverage is only 33% — `table` and `schema` have no descriptions at all — so the description should carry that load. It only implies the table must be a hypertable and says nothing about what schema means or how the two relate, leaving the agent to infer semantics for two of three required-ish inputs.

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 and resource (list the chunks of a TimescaleDB hypertable) plus the distinguishing payload (range_start/range_end, compression state). An agent can separate this from list_hypertables or list_partitions by the word 'chunks', though no sibling is named 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?

Gives a useful pre-condition outcome ('Empty list when the table is not a hypertable') that implies when the tool is applicable, but never says when to prefer it over list_hypertables, get_hypertable_stats, or list_partitions, and states no prerequisites or cost.

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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