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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely behavioral context beyond that: the fallback behavior when time is unknown (computed across every half hour, with per-field dependency flags). It does not note any cost/latency implications of that sweep, which keeps it from 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?

Three sentences, front-loaded with the action and inputs, followed by return contents and the one non-obvious edge case. No restatement of the name, no filler.

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?

No output schema exists, so the description carries the return-value burden and does so by enumerating the chart components and the card link. Combined with the fallback explanation, an agent has everything needed to call and interpret 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 100%, so baseline is 3; the description earns one more by explaining the semantic consequence of omitting birth_time and by characterizing time_zone as the birthplace zone, not the user's current zone. Format details (YYYY-MM-DD, HH:MM) are correctly left 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 specific verb and resource ('Calculate a person's Human Design chart') and immediately names the required inputs. The description also enumerates the domain outputs (type, strategy, authority, profile, definition, centers, channels, card link), so an agent knows exactly what it 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?

Clearly frames the main usage decision: supply birth_time when known, omit it when unknown, in which case a time-agnostic chart is computed. There are no sibling tools to route against, so the only real guidance needed is the optional-parameter condition, which is covered.

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