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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds one piece of behavioral context not in annotations - the 50-credit Tier 3 cost - but says nothing about auth needs, rate limits, or what the overlay does to the response shape.

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 tight sentences with the core action front-loaded, followed by the optional mode. The bracketed group/cost metadata is structured housekeeping rather than prose, so nothing is wasteful.

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 no explanation, and the input schema fully documents the birth-data, natal-overlay, fields and precision parameters. Purpose and cost are covered; only the usage/routing context is thin, which keeps it out of 5 territory.

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 object carries extensive field documentation (timezone semantics, houseSystem letter case, rejected short forms), so the schema does the heavy lifting. The description adds no parameter detail beyond mentioning that the natal overlay is optional, 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 and resource ('Calculate current Human Design transit activations') and names the optional natal overlay behavior, which is enough to separate it from the natal-chart sibling astroway_hd_human_design. It never names an alternative explicitly, 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 description explains what the overlay does but gives no when-to-use guidance, no prerequisites, and no routing against siblings such as astroway_mcp_ai_explain_transit or astroway_hd_group_overlay. The natal-overlay mode is described as a capability, not as a condition that selects this tool.

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