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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered without the description's help. The definition does add non-obvious operational context in the form of a credit cost and tier, which is genuinely useful for budgeting tool calls, but says nothing about the two-chart inputs, computation weight, or latency.

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 lines with zero filler and the core subject front-loaded, so nothing wastes space. However the brevity is under-specification rather than tightness — there is simply too little content for a tool of this complexity.

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?

This is a heavy tool: three nested birth-data objects, a compact-mode fields parameter, and a precision control. An output schema exists so return values need no explanation, but the description never mentions that two complete birth charts are required or how this differs from the other family/relational synastry tools, leaving a significant gap.

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 objects are documented in detail, so the baseline is 3. The description contributes nothing about sibling1/sibling2, the optional parent chart, precision, or fields, leaving all parameter meaning to the schema.

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 recognizable scope — synastry between siblings — but 'dynamics' is vague and the definition never distinguishes this from siblings such as astroway_family_parent_child_deep or astroway_relational_synastry. An agent gets the general subject but not the specific output this tool produces.

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 exclusions, and no named alternative among the many family/relational synastry siblings. The [Group: Family Astrology] tag implies taxonomy but gives no routing logic, so an agent must guess between this and the other family tools.

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