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

Annotations already declare readOnlyHint=true and destructiveHint=false, which establishes the safety profile. The description adds meaningful context beyond that: it discloses the full event set covered, the exact-instant refinement, the time ordering, and the significance scoring. It doesn't mention response size or execution time, but the listed behavior is transparent and aligns with a read-only forecast tool.

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?

Four sentences, no filler, and the core message is front-loaded. The first sentence gives the verb, resource, and window; the second enumerates coverage; the third defines the output; the fourth states use cases. Every sentence earns its place.

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?

For a read-only, single-request tool with no output schema, the description covers inputs, output, event scope, and purpose. The only missing piece is an explicit statement of the output shape or element structure, but the phrase 'time-ordered timeline' and the per-event enumeration make that reasonably inferable. A 5 would require more on output format.

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 all parameters well; baseline is 3. The description adds extra value by explicitly noting the 90-day cap (reinforcing startDate/endDate semantics) and by saying the timeline is significance-scored (connecting to minSignificance). This goes slightly beyond the schema without redundancy.

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 begins with a precise verb ('Forecast') and resource ('western astrology events for a single birth chart over a window up to 90 days'), then enumerates every event type covered: transit-to-natal aspects, sign ingresses, stations, eclipses, and New/Full Moons. It ends with a clear deliverable ('time-ordered, significance-scored timeline') and use cases, making it easy for an agent to distinguish from the sibling forecast tools.

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 concrete use cases ('Built for astrology forecast feeds, transit alerts, and timing tools') and explicitly scopes the window to 90 days. It does not name sibling tools like post_forecast_digest or post_forecast_timeline as alternatives, but the event-type enumeration and timeline description make it clear when this tool should be preferred.

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