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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds genuinely useful business context the annotations do not carry: the endpoint and a per-call cost of 10 credits (Tier 1). It says nothing about pagination, response shape, or how the combined output interleaves the three systems, but against annotations it is adequate.

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?

One front-loaded sentence plus bracketed metadata; nothing is padded. It is arguably too terse, but every element present earns its place and the core purpose leads.

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?

An output schema exists, so return values need not be described. But for a combined time-lord synthesis tool, the description leaves open what the stack actually reports and how targetAge interacts with the birth date, which is exactly the context an agent needs to call it instead of the three single-technique siblings.

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 nested birth-data schema is unusually detailed (timezone vs timezoneOffset rules, houseSystem letters, rejected short forms). The description adds nothing about parameters and does not explain the relationship between date and targetAge. Baseline 3 is correct when the schema does all the work.

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?

It names the three techniques it merges (profection, ZR, decennials) and the input it works from (a date), so the general function is inferable. However, 'ZR' is an unexpanded abbreviation and the description never distinguishes this aggregate from the sibling tools that each deliver one of these techniques individually (profections_detail, zodiacal_releasing_*, hand_decennials). It states a purpose but does not let an agent cleanly separate it from its neighbours.

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 when-to-use guidance, no prerequisites, and no mention of the individual profection/ZR/decennial tools as alternatives. An agent receiving this has to guess whether the combined stack or the single-technique sibling is the right call.

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