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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful non-schema facts—endpoint, credit cost of 100 (Tier 4)—but says nothing about auth, rate limits, or how the collective overlay is derived from the inputs.

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 followed by a compact metadata block (group, endpoint, required, cost) that earns its space by carrying cost and routing information. No filler or restated boilerplate.

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-shape explanation is not required, and cost/endpoint are covered. What is missing is the decision context for a tool that sits among several multi-person HD tools: no trigger conditions, no contrast with compatibility or penta, and only a vague hand-wave at what 'collectively defined centers and channels' means in the result.

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 coverage is 67% and the nested birth-data object is documented in depth by the schema itself. The description contributes only '2 or more people', which matches the array's minItems: 2, and '[Required: inputs]'; it explains nothing about fields, precision, or the per-person parameters.

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+resource ('Calculate a combined HD group overlay chart') and scopes it to '2 or more people, showing collectively defined centers and channels', which is enough to separate it from single-chart siblings. It does not explicitly name the nearest alternatives (compatibility, penta), so sibling differentiation is implied rather than stated.

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 never says when to pick this over astroway_hd_human_design_compatibility, astroway_hd_penta, or astroway_hd_hologenetic for a multi-person reading. The only adjacent guidance is the bracketed '[Required: inputs]' and cost tag, which are prerequisites, not usage conditions.

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