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

The description discloses the output structure (compact birth card plus long_range with specific fields), the cardinality (one theme card only), the edge-case handling (Feb-29 follows Postgres age(), error if as_of_date < birth_date). Annotations (readOnly, idempotent, non-destructive) align with the stated behavior.

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 concise yet comprehensive, covering purpose, usage, behavior, and edge cases in a few sentences. It avoids fluff and focuses on essential information, making it efficient for an agent to parse.

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?

Given the lack of an output schema, the description compensates by listing the output fields and their names. It also mentions the specific error condition. All necessary contextual details for using the tool correctly are present.

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 descriptions for both parameters are clear and meaningful: birth_date is described as 'Civil birth date YYYY-MM-DD' and as_of_date as 'As-of civil date YYYY-MM-DD'. The tool description adds context (e.g., birth_date resolves Cosmic birth card, as_of_date used for current journey year), and schema coverage is 100%.

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 tool's purpose: computing a 90-year Long Range Journey theme card from birth_date and as_of_date. It explicitly distinguishes from sibling tools like get_age_spread and get_date, ensuring no ambiguity.

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?

It explicitly states when to use the tool ('USE for one person's 90-year Long Range Journey theme card') and what not to use it for (not for age spread/plate or date/sky/calendar). This gives clear guidance relative to alternatives.

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