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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: the cost (10 credits, Tier 1), the endpoint, and the reduction method ('all letters, reduced'). It does not address rate limits or response caching, but for a stateless read calculation the disclosure is solid.

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 core sentence is front-loaded and dense with useful specifics; the bracketed metadata block is compact and scannable. Slight redundancy in restating required parameters that the schema already enforces, but nothing egregiously wasteful.

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 burden is low for a single-number calculation. The missing piece is disambiguation from the other expression tools across systems, plus any note on how 'date' participates in an expression-number calculation.

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' carry only type/pattern constraints. The description partially compensates by stating that the name is the full birth name (letters) and by echoing the two required parameters, but it never clarifies date semantics (birth date vs. event date) or name formatting rules. Baseline 3 is appropriate given partial coverage.

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 an unambiguous resource ('the Expression (Destiny) number'), and names the system ('Vedic system'), which separates it from the Chaldean, Kabbalistic, and Pythagorean variants in the sibling list. It also adds algorithmic scope ('from full birth name letters (all letters, reduced)'). It does not, however, contrast itself with those siblings in prose, relying on the name/group tag to do that work.

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 guidance on when to pick Vedic over Chaldean, Kabbalistic, Pythagorean, or the numk/numks/num-p equivalents of Expression, nor any exclusion or prerequisite. The only usage-adjacent content is the bracketed '[Required: name, date]' and cost line, which state constraints rather than selection criteria.

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