human_design_chart

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, but the description adds substantial behavioral context: it returns raw JSON, costs 2 credits per call (plus 2 more for visuals), rejects zone-less datetimes rather than assuming UTC because Human Design is minute-sensitive, and explicitly notes that the API handles the ~88° Design calculation automatically. These details go well beyond the annotations.

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?

The description is long but every sentence earns its place. It opens with the core purpose and outputs, then in a tight sequence covers the raw JSON format, the alternative tool, credit cost, the two-calculation-moment domain concept, the timezone rule with reasoning, and two concrete examples. There is no filler or repetition; the structure is front-loaded and logical.

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?

For a tool with no output schema, the description compensates by listing all major output categories. It covers inputs (including the timezone requirement and coordinate resolution), behavior (automatic design calculation, rejection of invalid datetimes), cost, and alternatives. It is complete for the complexity of a Human Design calculation tool, leaving no critical 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 coverage is 100%, but the description enriches parameters with crucial context: it explains why the timezone is required (an hour of error changes the Profile and Design Sun line), provides two full usage examples (one with local time + timezone, one with Z suffix), and instructs that latitude/longitude must be resolved via location_search, never recalled from memory. This adds meaning beyond the schema's bare descriptions.

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?

The description states the tool 'Calculate a full Human Design I Ching hexagram chart from birth data' and enumerates the exact outputs (Type, Strategy, Authority, Profile, Centers, Gates, Channels, Incarnation Cross, planetary positions). It also distinguishes itself from the sibling 'explore_human_design' by noting that alternative is for interactive bodygraphs. This is a specific, differentiated purpose.

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 explicitly says to use 'explore_human_design' instead for a user-facing interactive bodygraph, providing a direct alternative. It also gives concrete guidance on when to use timezone vs. UTC, warns against recalling coordinates from memory (use location_search), and explains the automatic handling of the two calculation moments. This is clear usage context with exclusions.

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