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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description's only extra behavioral fact is the cost line ('100 credits (Tier 4)'), which is genuinely useful for planning but is not expanded (no mention of what the cost scales with, e.g. period length).

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?

One tight sentence with the resource and its contents front-loaded, followed by three short bracketed metadata lines that carry real signal (group, endpoint, cost). No filler, though the endpoint/cost lines are boilerplate that could be trimmed or merged.

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 the input schema is fully described. Still missing: how the natal chart is used to produce the calendar (transits to natal vs general sky events?), what the temporal granularity of the output is, and the year-vs-period mismatch against the description.

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 natal chart fields, timezone rules, compact-mode 'fields' and 'precision' are all already documented in the schema; baseline is 3. The description adds nothing parameter-specific and its phrase 'for a given period' is actually looser than the schema, which takes a single integer 'year'.

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 (Generate) and resource (forecast calendar) and enumerates the four contents (transits, lunar phases, ingresses, retrograde stations), which lets an agent infer this is a superset of a plain transit calendar. However, it never names the sibling astroway_prognostics_transit_calendar, so the agent must infer the distinction rather than being told it.

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 / when-not-to-use guidance and no alternative is named, despite astroway_prognostics_transit_calendar sitting right next to it in the sibling list with an obviously overlapping purpose. 'For a given period' is also unhelpfully vague and does not match the schema's single required 'year' field.

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