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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds a genuinely useful non-schema behavior: the cost (100 credits, Tier 4), which lets an agent budget. It says nothing about result volume, date-range limits, or pagination.

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 structured group and cost tags. Nothing is padded, though the bracket metadata is arguably presentation rather than description.

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 not be described, and annotations cover the safety profile. The remaining gaps are the planet ID domain and any range/limit constraints, which are modest for a read-only query tool but still real.

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 only 33%, and the two documented parameters (fields, precision) are the optional ones. The description compensates for the undocumented required parameters by conveying their meaning (two planets plus a date range), but it never explains what a planet ID actually is or its valid domain, which is the key ambiguity for the caller.

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 a specific verb and resource: 'Find all conjunctions between two planets within a date range,' which tells an agent exactly what is computed. It adds the domain framing ('start of a new synodic cycle'), but it never distinguishes itself from close siblings such as astroway_calendar_aspects or astroway_aspects_aspect_timeline, so the agent must infer the boundary.

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?

There is no when-to-use guidance, no prerequisites, and no named alternative among the many calendar/aspect siblings. The phrase 'defining the start of a new synodic cycle' hints at the analytical intent but does not tell the agent when this tool is preferable to a generic aspect search.

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