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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely non-structured context: the credit cost (10 credits, Tier 1) and the group classification, which matters for budgeting calls across a large tool surface.

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 sentences plus bracketed metadata; the core purpose is front-loaded with zero filler. Slightly clipped, but nothing in it is wasted.

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 annotations cover the safety profile. The remaining gap is disambiguation from the strict/other-system Expression siblings in this very large tool family, which the description does not address.

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 not. The phrase "full birth name letters (all letters, reduced)" usefully disambiguates that `name` must be the complete birth name rather than a nickname, but the required `date` parameter is left entirely unexplained.

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 verb and resource ("Calculate the Expression (Destiny) number") and pins the system as Kabbalistic (phonetic), plus clarifies the input basis ("full birth name letters, all letters, reduced"). However it never distinguishes itself from the near-identical sibling astroway_numerology_kabbalistic_strict_expression, which an agent would need to choose between.

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, when-not-to-use, or alternative guidance. With five sibling Expression variants (chaldean, pythagorean, vedic, kabbalistic_strict, numks) an agent gets no routing signal beyond the name itself. Usage is only implied by the tool name.

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