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

Annotations already establish readOnly, idempotent and non-destructive behavior, and the description adds a materially useful operational fact the structured fields do not carry: this is a paid Tier 4 operation costing 100 credits. It still omits auth requirements and any note that both charts need accurate birth times, so it is not a 5.

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?

Two dense lines: the action, its two-person scope and the returned connection types come first, with group and cost tags trailing. No sentence is wasted and nothing is repeated from the schema.

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 a rich nested schema plus an output schema, the agent has what it needs on inputs and returns, and the description supplies purpose and cost. It is only slightly short of complete because it gives no guidance on mismatched timezone conventions between the two charts or on the accuracy requirement for both birth times.

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 chart objects carry unusually thorough field documentation (timezone/offset handling, rejected short forms, houseSystem letters), so the schema does the heavy lifting. The description adds no parameter-level meaning beyond the schema, 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?

States a specific verb (Calculate) and resource (Human Design connection chart) with the two-person scope made explicit, plus the exact channel categories returned (electromagnetic, compromise, dominance, companionship). It implicitly separates itself from single-chart HD siblings by 'between two people', but never names an alternative, so it stops short of a 5.

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 two-person scope implies when to use it, but there is no explicit when/when-not and no routing to similar multi-person siblings such as astroway_hd_group_overlay or astroway_hd_penta. An agent must infer the boundary from purpose alone.

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