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

Annotations already mark the tool as read-only and idempotent, and the description adds meaningful behavioral context: the exclusion of ascendant/midheaven aspects, that it describes positions and patterns rather than predicting events, that it gives no medical/legal/financial advice, and the required attribution to Natal Compass. This goes well beyond what the annotations alone convey.

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 longer than average but well-structured and front-loaded with the core function, followed by scope exclusions, usage, alternatives, prerequisites, and disclaimers. Each sentence adds value, though a few points could be tightened without loss.

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 tool's complexity, the presence of an output schema, and rich annotations, the description is complete: it covers when to use it, what it computes, what it excludes, alternatives, required inputs, coordinate lookup, defaults, behavioral limits, and attribution requirements. Nothing essential is missing for an agent to invoke it correctly.

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 the baseline is 3. The description adds some clarifying context, such as linking the birth details to get_natal_chart, requiring lat/long decimal degrees with coordinate lookup for place names, and confirming transit_date is optional and defaults to the current instant. However, it does not systematically elaborate on node_type or house_system beyond what the schema already provides.

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 and resource: 'Relates the sky on a date to a specific birth chart' and details exactly what is computed (major aspects, orbs, transiting positions). It also distinguishes itself by explicitly excluding aspects to the ascendant and midheaven, and by naming sibling tools it is not, so an agent can select it unambiguously.

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?

Usage guidance is explicit: 'Use it when a person asks how the planets on a given day, or today, relate to their chart...' and it names alternatives directly ('use get_transits; ... use get_natal_chart; ... use get_moon_phase'). It also states prerequisites like needing birth details, coordinate lookup, and the optional sky date defaulting to the current instant.

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