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

Annotations already establish readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description earns credit by disclosing the pricing tier (10 credits, Tier 1) and the deterministic scoring basis, which are real cost/behavior facts an agent needs before calling. It stops short of stating that both owner and pet charts are mandatory inputs.

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 short lines, outcome front-loaded before the group and cost metadata. Nothing is padding given how little it says.

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 explained, and the nested birth-data schema is exhaustively documented. Still, for a two-chart nested-input tool the description never confirms that both owner and pet charts are required or what the score means interpretively (e.g., what counts as compatible).

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?

With 100% schema description coverage, the schema already documents the owner/pet birth-data objects, timezone handling, fields and precision in depth. The description adds nothing about inputs, which is acceptable at baseline but not additive.

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 deliverable (a 0-100 compatibility score) and the method (element + sign distance), which is concrete. It does not explicitly contrast with the many relational synastry/match siblings, though the pet-scoped name and the phrase 'owner-pet' implicitly separate it.

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 statement of when to choose this over alternatives such as astroway_relational_match_score or the pet temperament tools, and no prerequisite guidance. The reader must infer usage entirely from the name and the scoring formula.

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