documentdb-query-optimizer

A guide for finding why Azure DocumentDB or MongoDB-compatible queries are slow and choosing suitable indexes. It uses query execution details, existing indexes, and sample documents to inform suggestions.

In plain words
What is it for?
Use it to investigate slow queries, review indexes, recommend an index, or improve general database performance when optimization is requested.
Why use it?
It replaces guesswork about slow queries with checks of how the database runs them and what data they access.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/azure/documentdb-agent-kit/query-optimizer
Any agent
npx skills add Azure/documentdb-agent-kit --skill query-optimizer
Clone the repo
git clone --depth 1 https://github.com/Azure/documentdb-agent-kit

Made for: Claude Code, Codex.

Per session 94 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,416 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00094 $0.02416
Opus 5 $0.00047 $0.01208
Sonnet 5 $0.00019 $0.00483
Haiku 4.5 $0.00009 $0.00242

Measured 2d ago against content hash 5744924df11e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

documentdb-query-optimizer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/query-optimizer/SKILL.md · 279 lines

How it starts

The opening of the file, as written. The whole thing — 279 lines — stays where its author put it; the contents beside it link to each section on GitHub.

DocumentDB Query Optimizer

When This Skill Is Invoked

Invoke only when the user wants:

  • Query/index optimization or performance help
  • Why a query is slow or how to speed it up
  • Slow queries on their cluster and/or how to optimize them
  • Index recommendations or index review

Do not invoke for routine query authoring unless the user has requested help with optimization, slow queries, or indexing.

High Level Workflow

Help with a Specific Query

If the user is asking about a particular query:

  1. Use list_indexes (MCP) or db.<coll>.getIndexes() (mongosh) to get existing indexes on the collection
  2. Use explain_operation (MCP) or .explain("executionStats") (mongosh) to get explain output with execution stats
  3. Use find_documents (MCP) or db.<coll>.findOne() (mongosh) to fetch a sample document to understand the schema

Then make an optimization suggestion based on collected information and best practices from the reference files. Prefer creating an index that fully covers the query if possible.

General Performance Help

If the user wants to examine slow queries or is looking for general performance suggestions (not regarding any particular query):

  1. Use list_databases (MCP) or show dbs (mongosh) to understand the database structure
  2. Use get_statistics with scope "collection" (MCP) or db.collection.stats() (mongosh) to identify large collections
  3. Use get_statistics with scope "index" (MCP) or db.collection.aggregate([{$indexStats:{}}]) (mongosh) to check existing index usage
  4. Use current_ops (MCP) or db.currentOp() (mongosh) to see currently running operations
  5. Suggest reviewing the most-used collections for missing indexes

MCP Tools Available

When DocumentDB MCP server is connected, these tools are available:

Tool name (exact) Description
list_indexes List all indexes on a collection — check if the query can use an existing index
explain_operation Run explain with executionStats for any operation (find, aggregate, count)
find_documents Fetch sample documents to understand schema — use with limit=1
get_statistics Get collection or index statistics (use scope: "collection" or "index")
current_ops Get currently running database operations
create_index Create a new index (only after user approval)
drop_index Drop an existing index (only after user approval)
sample_documents Sample random documents from a collection

Read the full file on GitHub · 279 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 279 lines · 94 tokens per session scan A 5744924df11e

Subscribe to this mod's changes

documentdb-query-optimizer is a skill published in the GitHub repository Azure/documentdb-agent-kit (5 stars, last pushed 1mo ago), licensed MIT. It adds 94 tokens to every session and 2,416 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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