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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds two traits beyond them: that a converse (reverse) direction is supported, and that the call costs 50 credits at Tier 3, which lets the agent weigh it against astroway_cost_estimate.

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 short sentences with the technique definition front-loaded, plus compact structured metadata lines for group and cost. Nothing is wasted, though the bracketed metadata is boilerplate rather than explanatory 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 and annotations cover the safety profile, so return values and safety need no explanation. The remaining gap is the one thing structured fields cannot supply: disambiguation from the closely related progressions tools, which the description leaves entirely to the reader.

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 schema already documents body, fields and precision in detail, including the converse flag and targetDate. The description adds no parameter-level meaning beyond what the schema provides, so the baseline 3 applies.

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 the parenthetical '(day-for-a-lunar-month)' defines the technique so the agent knows what is actually computed. However, it never distinguishes this from the sibling tools astroway_prognostics_progressions (secondary) and astroway_prognostics_minor_progressions, which is the main ambiguity in this tool family.

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 description gives no when-to-use guidance and names no alternatives, despite sitting in a dense prognostics family where progressions, minor_progressions, primary_directions and symbolic_directions are all plausible confusions. 'to a target date' implies a usage context but does not tell the agent when this technique is the right choice over its siblings.

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