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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond annotations: the credit cost (10 credits, Tier 1), the endpoint, and the required inputs. It does not disclose output format or any failure/validation behavior, but the output schema exists to cover returns.

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 operative sentence is front-loaded and zero-waste; the bracketed metadata lines are compact and scannable. Slightly redundant to repeat 'Required: name, date' which the schema already enforces.

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 annotations covering safety and an output schema covering returns, the description is nearly sufficient – cost and endpoint are helpful additions. Its main shortfall is the absence of any signal distinguishing it from the 'strict' kabbalistic variant, which is the one decision an agent actually has to make here.

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 50% – the required 'name' and 'date' have no schema descriptions, while 'fields' and 'precision' do. The description compensates only partially by stating that the day-of-birth digit drives the calculation and listing required params, but adds no format or range detail beyond the regex already in the schema. Baseline 3 fits.

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 Birthday number') and pins the variant with 'Kabbalistic (phonetic) system' and 'from the day-of-birth digit', which separates it from Chaldean/Pythagorean/Vedic birthday tools and from the kabbalistic_strict sibling. It does not, however, explain what makes it distinct from astroway_numerology_kabbalistic_strict_birthday beyond the 'phonetic' qualifier.

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?

No when-to-use, when-not-to-use, or alternative guidance is given. The bracketed metadata ('Required: name, date', cost) is administrative, not usage selection help, and nothing steers an agent between this and the many sibling birthday variants.

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