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

Annotations already establish readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered and the description is free to spend its words elsewhere — which it does, enumerating the returned artifacts and the API Pro gating. Minor tension: 'it needs a birth time' reads as mandatory while the schema makes time nullable (chart falls back to noon, time-dependent values withheld); not an annotation contradiction, but a small inconsistency worth flagging.

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, zero waste: the first front-loads the returned value, the second carries the trigger condition and prerequisites. The '(API Pro)' aside is the only non-essential token and it is genuinely informative about availability.

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?

There is no output schema, and the description does the right thing by enumerating the payload (angles, planets with orbs, per-sphere scores, overall score). Inputs and prerequisites are covered, so what remains missing is minor — no mention of failure modes for unknown/ambiguous places.

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 description only tells the agent it needs 'a birth time and the place's coordinates', which is a restatement of the two required top-level objects rather than added meaning. The nested birth/location fields do carry their own schema descriptions (time semantics, timezone resolution, historical DST), so the schema does most of the work and a baseline 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?

Names a specific computation (relocated astrocartography angles, planets on them with orbs, per-life-sphere and overall scores) for a precisely bounded scope: one place against one chart. The 'one place against one chart' phrasing implicitly separates it from the multi-place sibling best_cities, so an agent can route without opening either schema.

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?

Gives an explicit trigger: 'Use it when the user asks whether a specific city or place suits them,' plus the prerequisite inputs. It stops short of naming the alternative (best_cities) or stating when-not to use this tool, so the routing guidance is clear but not exhaustive.

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