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

Beyond the readOnly/destructive annotations, the description reveals meaningful behavior: it returns components rather than a verdict, the ties are either present or absent, and the scoring weights are always included so a caller can re-derive or replace the composite score. This materially shapes caller expectations and adds value beyond what annotations alone provide.

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?

The description is three sentences with no redundancy. The first sentence front-loads the operation, output philosophy, and response components; the second gives use cases; the third adds a valuable reproducibility guarantee. Every sentence earns its place.

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 no output schema, the description compensates well by describing the response's major parts: nawals, coefficients, trecenas, five ties, weights, and composite score. The parameter schema is rich, so invocation is well covered. It stops short of naming the five ties or exact field shapes, which prevents a perfect score.

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%, so all six parameters — including correlation and directionScheme — are already documented in the input schema. The description adds no parameter-level detail, which is acceptable because the schema carries the full semantic burden. 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 opens with a specific verb and resource: Mayan compatibility between two birth dates. It differentiates this from sibling endpoints by emphasizing that results are 'published as its parts rather than as a verdict' and enumerates the exact response components (nawals, coefficients, trecenas, five structural ties, weights, composite score), making the tool's identity unmistakable.

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 description gives clear intended contexts: 'matchmaking features, relationship reports and compatibility widgets that need to show their working.' This tells an agent when the tool is appropriate, though it does not explicitly name alternative sibling tools or state when not to use this endpoint.

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