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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered structurally. The description adds genuinely useful behavior beyond that: the endpoint (POST /v1/match/score), the cost (50 credits, Tier 3), and the fact that one call replaces a multi-call workflow — which matters for cost-aware planning. It does not discuss latency or auth, keeping it at a solid 4 rather than 5.

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?

Front-loaded with the tool's identity and output payload in the first sentence, followed by the positioning rationale and the input note. The bracketed Group/Endpoint/Required/Cost block is structured metadata rather than prose, and no sentence is redundant.

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 explanation, and the input schema fully documents the nested chart objects. The description still supplies the selection-critical facts an agent needs — what the aggregate returns, what it replaces, the endpoint, the credit cost, and the shared input shape — leaving no material gap for calling it correctly.

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% and the nested TwoChart object is exhaustively documented, so the schema carries the parameter burden and 3 is the baseline. The description adds only 'Same TwoChart input as /synastry', which is orientation rather than new field-level semantics; the fields/precision compaction parameters are left entirely to the schema.

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 concrete verb+resource — a one-call dating-compatibility aggregate over the synastry engine — and enumerates the exact outputs (overall 0-100 score, label, harmony/tension, attraction score, influential cross-aspects, green/red flags). It also distinguishes itself from the constituent siblings by naming what it replaces (synastry + attraction + custom flag logic), so an agent can tell it apart from astroway_relational_synastry and astroway_relational_synastry_attraction_score.

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 'Built for dating apps that want a single call instead of synastry + attraction + their own flag logic' clause gives a clear selection condition against the sibling tools, and 'Same TwoChart input as /synastry' tells the caller the input contract is shared. It stops short of explicit when-not guidance or naming the sibling tool identifiers directly, so it is clear context rather than full routing.

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