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

Annotations already indicate readOnlyHint=true, and the description adds details about the return value: structured reading including shared core numbers and text interpretations for various aspects. No contradictions with annotations.

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, front-loaded with purpose, and provides essential information without unnecessary details. Every sentence adds value.

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?

Given no output schema, the description adequately explains what the tool returns. Parameters are fully covered in the schema. For a read-only tool with few dependencies, the description is complete.

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 coverage is 100%, so all three parameters are already documented with descriptions. The description adds context about the date format (DD-MM-YYYY) and locale options, but does not significantly enhance understanding beyond the schema. Baseline is 3.

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 clearly states the tool calculates relationship compatibility using the Destiny Matrix numerology method from two birth dates. The verb 'calculate' and resource 'compatibility' are specific, and it distinguishes from the sibling tool 'calculate_matrix' which likely handles single individuals.

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 explicitly says 'Use this when a user asks how compatible two people are, or wants a numerology compatibility reading based on two birth dates.' This provides clear context for when to use the tool. It does not explicitly state when not to use it, but the sibling tool name implies an alternative for single-person calculations.

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