calculate_synastry

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

Annotations already declare readOnly, idempotent, and non-destructive behavior, so the bar is lower. The description adds useful expectations by stating it returns 'factual inter-chart data without compatibilty scores or relationship conclusions,' which prevents the agent from expecting judgmental output.

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 short sentences with no filler. The primary purpose is front-loaded, and the second sentence adds the important output caveat. Every word earns its place.

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?

Given the rich input schema, output schema, and strong annotations, the description covers the essential purpose and behavioral boundary. It does not explicitly guide edge cases like unkown_time or sibling selection, but those are not critical for basic invocation.

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?

The input schema provides 100% coverage with detailed descriptions for person_a and person_b and all nested fields. The description adds no new parameter-specific detail, but the schema already carrries that burden.

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 uses a specific verb ('Calculate') and resource ('structured synastry relationships between two birth charts'), making the tool's core purpose clear. It also states the output style ('factual inter-chart data') but does not explicitly name or differentiate from sibling tools like calculate_aspects.

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 phrase 'between two birth charts' implies the tool is for comparing two charts, but the description gives no explicit when-to-use versus alternatives or exclusions. Usage guidance is only implied, not stated.

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