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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial behavior beyond them: exactly 8 of 20 checks are evaluated and 12 are not under this source profile, per-check states are matched/not_matched/not_evaluated/unavailable with explicit coverage, unknown states are not absence, and counteractions are never evaluated. That is exactly the kind of non-obvious operational detail an agent needs.

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 output/content description is front-loaded before the caveats, and every sentence carries information rather than filler. It is dense and somewhat run-on with compressed jargon, but nothing is wasted for a tool whose contract is genuinely complex.

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?

With no output schema, the description carries the burden of explaining return values and does so well by naming the four check states and the coverage/unknown-state semantics, plus a clear scope limitation (no age estimate or verdict). The remaining gap is that the relationship to the sibling get_longevity is never stated.

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%, so all seven parameters including the gender enum and its classical-yoga rationale are already documented in the schema. The description adds no parameter-level syntax, defaults, or format information beyond it, which is the baseline 3 case.

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 gives a specific verb and resource ("Return schema 1 natal D1 longevity_reference") and enumerates the content it carries: engine revision, effective basis, the BPHS-43 three-pair method and HPA-XIV positional checks. It is specific about what the tool does, but the jargon ("schema 1 natal D1") is opaque and it never distinguishes itself from the sibling get_longevity, so an agent must infer the division of labor.

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 statement of when to pick this tool over get_longevity or any other sibling, and no prerequisites are given. The interpretive caveats (not to be read as lifespan/death) describe the output's limits rather than the conditions that select this tool, so they do not substitute for selection guidance.

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