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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-redundant context: the cost (50 credits, Tier 3) and the fact that the output is a weighted composite over a fixed set of contact types, which tells the agent the result is deterministic for a given pair of charts. It stops short of describing latency or credit-refund behavior.

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?

A single front-loaded sentence names the weighting and the constituent contacts, followed by two compact metadata tags for group and cost. Nothing is padded or repeated, though the tags are terse enough that they read as structured metadata rather than prose.

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?

With an output schema present, the description need not explain return values, and annotations cover the safety profile. What remains missing is routing guidance against the many sibling synastry/relationship tools. Given the rich nested input schema and cost disclosure, the definition is close to complete but leaves sibling disambiguation to the caller.

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 100%, with chart1/chart2 carrying extensive prose about timezone handling, house-system letters, and rejected shorthand field names, plus the fields and precision compact-mode parameters. The description adds nothing beyond what the schema already says, so the baseline 3 applies.

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 precise verb-and-resource outcome: a weighted 0–100 attraction score derived from named synastry contacts (Sun-Moon, Mars-Venus, ASC/DSC, etc.) and the 5th-house overlay. That is far more specific than the title alone. It does not, however, differentiate itself from the near-identically named sibling astroway_rel_synastry_attraction_score or from astroway_relational_match_score, so an agent cannot tell which of the two attraction/match variants to pick.

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 alternatives named despite several overlapping siblings (relational_match_score, rel_synastry_attraction_score, relational_synastry). The agent must infer the selection criteria entirely from the tool name and score composition.

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