on_this_day

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

No annotations are provided, so the description bears full burden. It fails to disclose key behaviors: what is returned (entries? count?), whether current year entries are included, authentication needs, or side effects. The poetic second sentence adds no behavioral info.

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 first sentence is clear and concise. The second sentence is poetic and does not add practical value; it could be replaced with more useful information. Overall, it is acceptably concise.

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 tool is simple (one parameter, no output schema), but the description omits output format and fails to distinguish from 'get_day' (which also retrieves entries for a date). Without annotations, more detail is needed for a retrieval tool.

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 100% and the parameter description in the schema already covers 'today', 'yesterday', and YYYY-MM-DD. The tool description does not add meaning beyond what the schema provides, so baseline 3 is appropriate.

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 clearly states the specific action ('resurface entries') and resource ('same calendar date in past years'), and adds the poetic but distinct 'true anniversaries' phrase that distinguishes it from sibling tools like 'get_day' or 'search'.

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 implies usage context ('same calendar date in past years') but does not explicitly state when to use this tool versus alternatives like 'get_day' or 'range'. No exclusions or when-not-to-use guidance is provided.

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