Skip to main content
Glama
Sign In
postgres-dba-mcp

postgres-dba-mcp

by a-lafon
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Go
Hybrid

explain_query

Read-only

Shows PostgreSQL query execution plans and cost estimates; optionally runs queries for real statistics and simulates hypothetical indexes to guide tuning.

Instructions

Explains the execution plan for a SQL query, showing how the database will execute it and provides detailed cost estimates. Queries with $n parameters get a generic plan.

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": {
      "sql": "<sql>"
    },
    "name": "explain_query"
  }
}

Input Schema

NameRequiredDescriptionDefault
sqlYesSQL query to explain
analyzeNoWhen True, actually runs the query to show real execution statistics instead of estimates. Takes longer but provides more accurate information.
verboseNoWhen true, returns the full PostgreSQL text plan instead of the summary.
hypothetical_indexesNoA list of hypothetical indexes to simulate. Each index must be a dictionary with these keys: - 'table': The table name to add the index to (e.g., 'users') - 'columns': List of column names to include in the index (e.g., ['email'] or ['last_name', 'first_name']) - 'using': Optional index method (default: 'btree', other options include 'hash', 'gist', etc.) Examples: [ {"table": "users", "columns": ["email"], "using": "btree"}, {"table": "orders", "columns": ["user_id", "created_at"]} ] If there is no hypothetical index, you can pass an empty list.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.2/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is largely covered. The description adds one real behavioral fact (parameterized queries yield a generic plan), but it does not warn that analyze=true actually executes the query, which is the one behavior an agent most needs flagged before running EXPLAIN ANALYZE on a mutating statement.

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?

Two short sentences, front-loaded with the core action, with no filler. The trailing 'generic plan' sentence is terse to the point of ambiguity about what the agent should do differently, but it is still efficient.

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?

With no output schema, the description carries the burden of describing returns and does so only at a high level ('execution plan', 'detailed cost estimates') without indicating what the plan structure looks like or when verbose output is needed. Adequate for a query-analysis tool but not complete.

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?

Schema description coverage is 100%, so the schema already documents sql, analyze, verbose, and hypothetical_indexes thoroughly. The description adds only the $n-parameter generic-plan note, which is marginal beyond structured data; baseline 3 is appropriate.

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 ('Explains the execution plan for a SQL query') and adds what the output contains (how the database will execute it, cost estimates). This is clearly distinct from execute_sql, though it does not name any sibling to sharpen the boundary.

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

Usage Guidelines2/5

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

There is no when-to-use guidance: nothing says to call this before or instead of execute_sql, analyze_query_indexes, or get_top_queries. The only conditional statement concerns parameterized queries getting a generic plan, which is a limitation note rather than usage guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server

Other Tools