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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context in the form of a cost (10 credits, Tier 1) and the backing endpoint, but says nothing about rate limits, auth requirements, or how the 10-year window behaves at the schema's 2100 upper bound.

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?

Front-loaded with the core behavior in one sentence, followed by compact bracketed metadata (group, endpoint, required, cost). Nothing is padded, though the bracket block is closer to boilerplate than prose.

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-value explanation is not required, and annotations cover safety. What's missing is routing context among the many BaZi siblings (year vs decade vs luck pillars) and any note on the `language` parameter, leaving the definition merely adequate for a 4-parameter, credit-consuming call.

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%: `fields` and `precision` are documented in the schema, while `language` and `startYear` are not. The description only repeats '[Required: startYear]' (already in the schema's required array) and adds no semantics for `language` or the decade windowing, so it fails to compensate for the coverage 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 first sentence names a concrete output (10 consecutive year pillars) and the input that drives it (a starting year), so an agent knows exactly what it gets. It does not, however, distinguish itself from the close sibling astroway_bazi_year_pillar (single year) or explain why one would want the decade form over repeated single calls.

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 guidance, no mention of the single-year sibling, and no stated prerequisites or exclusions. The bracketed '[Required: startYear]' restates the schema rather than advising usage.

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