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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, indicating a safe read operation. The description adds the date-range scoping, but this is also evident from the schema parameters. It does not disclose additional behavioral details like pagination or result ordering, but the output schema covers return values.

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 that states the action and resource without any redundancy. It is efficient and every word contributes to understanding the tool's 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?

For a simple read-only list tool with rich annotations, full schema coverage, and an output schema, the description is fully adequate. It does not need to explain return values because the output schema exists, and the safety profile is already declared by the annotations.

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 input schema provides 100% coverage with detailed parameter descriptions, including the date/time format for start and end. The description's mention of 'within a date range' and 'for a baby' simply restates the schema parameters without adding new meaning. The baseline of 3 applies because the schema does the heavy lifting.

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 'List' to identify the action, and clearly specifies the resource as 'diary/journal entries' with scoping to a baby and date range. This distinguishes it from sibling list tools like list_feeds and list_sleep, which handle different resource types.

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 description clearly implies when to use this tool (to list diary entries for a specific baby within a date range), but it does not explicitly state when not to use it or name alternatives. However, the sibling tool list and the clear resource scope provide sufficient context for an agent to select this tool appropriately.

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