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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description's only extra behavioral fact is the 100-per-call cap, which is already expressed in the schema as maxItems=100, so it adds little. Nothing is said about append-vs-replace semantics, duplicate handling, per-item validation failures, or behavior when the dataset is at capacity.

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 front-loaded sentence with the verb and scope up front and no filler. The parenthetical limit is the only wasted clause since it merely restates the schema's maxItems.

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 two-parameter additive mutation with no output schema, an agent still lacks key facts: what the call returns (e.g., created item IDs or a count), whether the operation is atomic across the batch, and how partial failures are reported. The annotations cover reversibility, so the remaining gap is moderate rather than severe.

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 50% — only datasetId carries a description ('Dataset UUID'), while the items array and its input/output fields are undocumented. The description partially compensates by naming the 'input/expected-output' pairing, which hints that output is the expected value, but it never states that output is optional or that input/output are arbitrary objects.

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?

States a specific verb (add) and resource (manual input/expected-output cases into an evaluation dataset) with a scope limit. It is clearly distinguishable from dataset_item_update and dataset_item_delete, though it does not name them explicitly.

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?

The word 'manual' implies this is for hand-authored cases rather than generated ones, which is an implied usage cue. There is no explicit when-to-use vs. dataset_item_update (editing existing items) or vs. creating a dataset first, and no prerequisites such as whether the dataset must exist or be empty.

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