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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely useful context the annotations lack: a credit cost (10 credits, Tier 1) and the reduction rule for the input letters. It does not contradict the annotations, but it says nothing about output shape or latency beyond cost.

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 compact sentences with the calculation rule front-loaded and the metadata brackets clearly separated. Nothing is padded, though the group/cost tags are administrative rather than descriptive.

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 explanation, and the read-only annotations cover behavior. What is missing is any justification for the required date parameter and any indication of how this result differs from the other expression-number variants, which matters given ~80 siblings.

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 50%: fields and precision are documented in the schema, while name and date are bare. The description compensates partially by clarifying that name means the full birth name with all letters reduced, but it never explains why the required date parameter is needed for an expression calculation, leaving a real gap.

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 gives a specific verb (Calculate) and resource (Expression/Destiny number) and states the input scope precisely: 'full birth name letters (all letters, reduced)'. The 'Pythagorean system' tag distinguishes it from the many Chaldean, Kabbalistic, and Vedic siblings, though no sibling is named explicitly.

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 or when-not-to-use guidance, and no routing to alternatives such as astroway_numerology_chaldean_expression or astroway_numerology_vedic_expression. The system name implies the domain, but the agent must infer selection entirely from the tool name.

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