Retrieve MongoDB collection statistics—document count, data, storage, and index sizes, average document size, and capped flag—to inspect collection storage usage.
Document count, data / storage / index sizes (MB), average document size, index sizes, capped flag.
| Name | Required | Description | Default |
|---|---|---|---|
| database | No | ||
| collection | Yes | ||
| connection | No |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds value by enumerating the actual metrics returned (data/storage/index sizes in MB, average document size, capped flag), which matters because there is no output schema. It does not say whether it errors on a missing collection or how expensive the call is.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
One short fragment with no padding, but it is not a sentence and lacks a leading statement of what the tool does, so the return-value list is doing double duty as the purpose.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Because there is no output schema, listing the returned metrics is genuinely useful, but the definition still leaves an agent unsure how to supply database and connection, or whether the call targets one collection by name. A collection-scoped read tool needs at least that much.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0% across three parameters (database, collection, connection), and the description says nothing about any of them — not that database/connection are optional with defaults, nor what they resolve to. With low coverage the description is expected to compensate and does not.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description is a noun-phrase list of returned metrics rather than a verb+resource statement; combined with the name collection_stats an agent can infer it reports statistics for a collection, but the description itself never says 'returns stats for a collection'. It does distinguish itself from count_documents by enumerating storage/index/capped info, which count_documents would not provide.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No when-to-use guidance at all: nothing says to prefer this over count_documents for document counts, or over server_status / list_collections. No mention of prerequisites such as which database or connection is targeted.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.