list_databases

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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile needs no restating. The description does add value beyond that: results are privilege-filtered per login and include on-disk size, which tells the agent to expect a possibly partial list. It says nothing about ordering, pagination, or what an empty/denied result looks like, so a 3 is right.

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?

A single well-formed sentence with the resource, the returned attribute, and the visibility constraint front-loaded. No filler, nothing repeated from the annotations or schema.

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?

For a simple read-only enumeration with full annotation coverage and no output schema, the description covers the essentials of what is returned. However, the connection parameter is undefined and the size metric's units/format are unspecified, both of which an agent needs before calling. Adequate but with clear gaps.

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% and the single parameter ("connection") is never mentioned in the description. An agent gets no explanation of what a connection refers to, whether it can be omitted, or how the nullable default is resolved. With low coverage the description was expected to compensate, and it 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?

Names a specific verb and resource ("List databases") and adds two distinguishing facts: results include size on disk and are filtered to those visible to the login. The resource alone clearly separates it from siblings like list_collections and list_indexes. It stops short of explicitly naming the nearest alternative, so it lands at 4 rather than 5.

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?

There is no statement of when to use this versus list_collections, collection_stats, or server_status, and no prerequisites or ordering advice. The parenthetical scope note ("only the ones the login may see") hints at a discovery use case but is a scope constraint, not usage guidance. An agent must infer that this is the top-level enumeration call.

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