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

With no annotations, the description carries the full burden. It discloses the method ('Steps through positions and refines by bisection') and accuracy ('accurate to the minute'), which is useful. However, it does not specify the output format (e.g., list of timestamps, dates with timezones), edge cases (e.g., no aspect in range), or any prerequisites (e.g., planet_a != planet_b). For a calculation tool, this is a moderate gap.

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 sentences, no waste. The first sentence states the core purpose and lists the aspect types; the second explains the method and adds the extra applications. The essential information is front-loaded and every clause 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?

The tool has 6 parameters, 5 required, and no output schema. The description explains the method but does not describe what the function returns (e.g., a list of timestamps, dates, or objects) or how the tz_offset_minutes parameter affects the output. It also doesn't mention what happens when no aspect occurs in the given period. These gaps leave an agent uncertain about expected results and error handling, making it incomplete for a tool of this complexity.

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 already has 100% coverage – every parameter (to, from, aspect, planet_a, planet_b, tz_offset_minutes) has a description with enums and constraints. The tool description adds no extra meaning beyond the schema; it only reinforces the purpose. Since the schema does the heavy lifting, a baseline of 3 is appropriate.

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 opens with a specific verb ('Finds') and a clear resource ('moments when two planets form an exact angle'), listing the exact aspect types. It is immediately distinguishable from siblings like planet_positions (which give positions at a time) and moon_state (which gives lunar phases) by focusing on exact timing of angular relationships.

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 implies when to use it: when you need exact moments (accurate to the minute) and notes that mean formulas are 'unfit' for these events. It doesn't explicitly name an alternative tool, but the context makes it clear this is for precise ephemeris calculations rather than approximate positions. It could be stronger by explicitly stating 'use for exact aspect times, not for general position queries'.

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