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

Annotations already declare this is a read-only, idempotent, non-destructive, closed-world call, so the safety profile is covered. The description adds genuinely non-redundant context: the converse-direction mode and, notably, the cost (50 credits, Tier 3) and endpoint, which matter for an agent budgeting calls. It stops short of describing output shape or pagination, but the output schema covers 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?

Two front-loaded sentences state what it computes and the direction option, followed by compact bracketed metadata for group, endpoint and cost. No sentence is wasted, though the technique definition in parentheses could arguably be tightened.

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 an output schema present and 100% parameter documentation, the description need not explain return values or input formats. It covers purpose, direction mode and cost, leaving only sibling differentiation and usage routing unaddressed for a tool family crowded with similar progression techniques.

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 parameters (including the richly documented body, fields and precision) are already fully specified structurally, and the baseline is 3. The description only incidentally touches the converse flag and adds no syntax or format detail beyond the schema.

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 (tertiary progressions) and even defines the technique's rate (day-for-a-lunar-month) and scope (to a target date). This distinguishes it from a generic 'progressions' tool, but it never names the closely related siblings (progressions, minor_progressions, symbolic_directions) that an agent must 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?

The only usage-relevant detail is 'to a target date' and 'supports converse direction'; there is no statement of when to pick tertiary progressions over secondary/minor progressions, primary directions, or profections, and no prerequisites or exclusions. An agent must infer the selection from the name alone.

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