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 two genuinely useful behavioral facts beyond that: a 50-credit Tier 3 cost, which lets an agent budget calls, and support for the converse direction, which changes how results are interpreted. It does not describe output shape, but an output schema exists.

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 sentences, front-loaded with the technique definition, followed by compact group/endpoint/cost metadata. Nothing is wasted, though the bracketed metadata lines are structural boilerplate rather than prose that helps selection.

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?

Parameters are fully documented in the schema and an output schema exists, so return values need no explanation. The remaining gap is purely usage-level: nothing tells the agent how this differs operationally from the other progression-style tools in the same family.

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 100%, so the baseline is 3. The description's 'to a target date' and 'converse direction' gesture at targetDate/targetTime/targetTzOffset and converse but add no syntax, format, or default information beyond what the schema already spells out in detail.

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 (Calculate) and resource (minor progressions), and the parenthetical 'lunar month-for-a-year' defines the technique precisely enough to distinguish it conceptually. It never names the confusable siblings (progressions, tertiary_progressions), so an agent must infer which progression variant to pick from the name alone.

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?

Says 'to a target date', which implies a forecast-style use, but there is no when-to-use guidance, no prerequisites, and no routing against the several progression siblings (major progressions, tertiary progressions, symbolic directions). The agent gets the technique name and nothing about when this one is the right choice.

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