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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description still adds real context: the return shape, the per-pair astro.com orb matrix methodology, the fact that it shares calcAspects() with the chart endpoint, and an explicit cost of 10 credits (Tier 1), which is not derivable from the schema or 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?

Two tight sentences: the first gives the output contract and methodology, the second the differentiating trade-off. The bracketed group/endpoint/required/cost block is scannable metadata with no filler, and the most important content (what it returns, why it differs) is front-loaded.

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 no prose, and the annotations cover the safety profile; the description also supplies endpoint, required params and cost. However, for a 15-parameter tool with only 33% schema coverage, the description does not close the gap on the ~10 undocumented inputs, leaving an agent reliant on inference for options like houseSystem and zodiacType.

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 description coverage is only 33% across 15 parameters, so the description carries a compensation burden it does not meet. It merely restates the four required params (date, time, latitude, longitude) already marked required in the schema and adds nothing about undocumented fields such as zodiacType, houseSystem, cosmogram, name, or city, nor does it explain the compact-mode interaction of fields/precision.

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?

States a specific verb and resource ('standalone aspect calculation: full inter-planetary aspect list') and names the exact returned fields (type / exactAngle / orb / isApplying). It also carves itself out from the general chart endpoint ('same calcAspects() as /chart but without planet positions / houses / midpoints overhead'), though it does not distinguish itself from the many other aspect siblings such as parallel_aspects or moon_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 'standalone ... without planet positions / houses / midpoints overhead' implies a when-to-use case (call this when you only need aspects, not a full chart), but there is no explicit statement of when to prefer this over siblings like astroway_calendar_moon_aspects or astroway_aspects_parallel_aspects. Usage is inferable rather than stated.

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