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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds the cost tier (100 credits, Tier 4) and endpoint, which is genuinely useful for an agent budgeting calls, but says nothing about invocation constraints, response size, or the practical distinction of a 100-credit calculation.

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 front-loaded sentence stating the analysis and its outputs, followed by terse structured metadata (group, endpoint, cost). Every line earns its place; only the absence of any routing sentence keeps it from a 5.

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 and full annotations present, the description need not explain return values, and the cost line adds useful context. It remains thin on routing and scope, however: the 'upcoming eclipses' framing is not reconciled with the year/yearsRange inputs, and the overlap with eclipse-listing and eclipse-rendering siblings is left unresolved.

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 body, fields and precision are already fully documented, and the baseline is 3. The description adds no parameter-level information at all — notably it never hints that a location point and year are required alongside the natal data, leaving that entirely to 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?

The description gives a specific verb and resource ('Analyse the impact of upcoming eclipses on a natal chart') and enumerates the outputs (aspects to natal planets, house activations, Saros series context), so the agent knows exactly what it produces. It does not, however, name or distinguish itself from close siblings such as astroway_calendar_eclipses or astroway_render_eclipse_path.

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 natal-chart framing implies the usage context (interpreting eclipses for an individual chart rather than listing eclipse dates), but there is no explicit when-to-use, when-not-to-use, or named alternative. The agent must infer the boundary against calendar_eclipses on its own.

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