MongoDB Agent Skills is an official collection of skills and plugins that help AI coding agents work with MongoDB databases, including Atlas and self-managed deployments. Developers use it for query writing, schema design, query optimization, Atlas Search, and vector search. The catalogue entries are MongoDB’s own agent skills, plugins, and setup instructions.
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.
npx agentmods add skills/mongodb/agent-skills/mongodb-query-optimizernpx skills add mongodb/agent-skills --skill mongodb-query-optimizergit clone --depth 1 https://github.com/mongodb/agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/mongodb/agent-skills/mongodb-query-optimizer)<a href="https://agentmods.dev/skills/mongodb/agent-skills/mongodb-query-optimizer"><img src="https://agentmods.dev/badge/skills/mongodb/agent-skills/mongodb-query-optimizer.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00098 | $0.02390 |
| Opus 5 | $0.00049 | $0.01195 |
| Sonnet 5 | $0.00020 | $0.00478 |
| Haiku 4.5 | $0.00010 | $0.00239 |
Grade A, and why
mongodb-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 6d 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.
This is a copy
100% identical to mongodb-query-optimizer — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MongoDB 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
Do not invoke for routine query authoring unless the user has requested help with optimization, slow queries, or indexing.
High Level Workflow
General Performance Help
If the user wants to examine slow queries, or is looking for general performance suggestions (not regarding any particular query):
- Use MongoDB MCP server atlas-get-performance-advisor tool to fetch slow query logs and performance advisor output
- Make suggestions based on this information
If Atlas MCP Server for Atlas is not configured or you don’t have enough information to run atlas-get-performance-advisor against the correct cluster, tell the user that general performance analysis requires Atlas MCP Server configuration with API credentials, and suggest they configure it or ask about a specific query instead.
Help with a Specific Query
If the user is asking about a particular query:
- Use collection-indexes, explain, and find MCP tools to get existing indexes on the collection, explain() output for the query, and a sample document from the collection
- Use atlas-get-performance-advisor MCP tool to fetch slow query logs and performance advisor output
Then make an optimization suggestion based on collected information and MongoDB best practices and examples from reference files. Prefer creating an index that fully covers the query if possible. If you cannot use MongoDB MCP Server then still try to make a suggestion.
MCP: available tools
How to invoke. Call the MongoDB MCP server with the exact tool name as toolName and a single arguments object as arguments. Do not pass the tool name as an option, query param, or nested key; pass it as the MCP tool name and the parameters as the arguments object. Full MCP Server tool reference: MongoDB MCP Server Tools.
What ships with it
4 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.
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.
- 6d ago First seen · 150 lines · 98 tokens per session scan A 62a5bff5f405
mongodb-query-optimizer is a skill published in the GitHub repository mongodb/agent-skills (181 stars, last pushed 3d ago), licensed Apache-2.0. It adds 98 tokens to every session and 2,390 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to mongodb-query-optimizer, differing in 0 lines, and is treated as a copy.
Other skills, from other repositories
mongodb-atlas-checker
Verify MongoDB Atlas setup and configuration for backend applications. Checks connection strings, environment variables, connection pooling, and ensures proper setup for Next.js and NestJS applications. Use when verifying MongoDB Atlas setup, checking connection strings or environment variables, or troubleshooting…
mongodb-migration-expert
Database schema design, indexing, and migration guidance for MongoDB-based applications. Use when adding or changing MongoDB collections, indexes, or fields, designing schema for multi-tenant or large datasets, or planning forward-only migrations.
database-schema-design
Use when designing database schemas, creating migrations, modeling data relationships, optimizing database queries, adding indexes, or selecting between SQL and NoSQL storage.
deprecation-and-migration
Manages deprecation and migration. Use when removing old systems, APIs, or features. Use when migrating users from one implementation to another. Use when migrating a database schema in production, such as renaming or dropping a column without downtime (expand/contract). Use when deciding whether to maintain or sunset…
nosqli
NoSQL injection — MongoDB operator injection ($ne, $gt, $where, $regex), CouchDB / Firebase / Redis attack patterns, auth bypass, blind extraction.
mongodb-natural-language-querying
Generate read-only MongoDB queries (find) or aggregation pipelines using natural language, with collection schema context and sample documents. Use this skill whenever the user asks to write, create, or generate MongoDB queries, wants to filter/query/aggregate data in MongoDB, asks "how do I query...", needs help with…