findOne

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

The annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint), but the description adds no additional behavioral context. There is no mention of what happens if multiple documents match, whether a null result is returned when no document is found, or any error semantics.

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?

The description is a single, front-loaded sentence with no redundant filler. It is appropriately sized for a simple read tool.

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?

The complete schema and annotations make the tool minimally usable, but the description leaves unspecified the return contract and behavior for non-matches or multiple matches. Since there is no output schema, a brief note about the returned document or null would improve completeness.

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?

The schema has 100% description coverage for all three parameters (filter, collection, projection), so the schema itself documents the parameters. The description adds no further parameter-specific meaning, so the baseline score applies.

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 uses the specific verb 'Find' and specifies the resource as 'a single document in a MongoDB collection.' The word 'single' clearly distinguishes it from the sibling tool find, making the tool's scope immediately obvious.

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 guidance on when to use findOne versus the sibling find, aggregate, or count tools, and no exclusions or conditions are provided. The intended use-case is only implied by the word 'single.'

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