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

Annotations already declare the tool read-only, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds meaningful behavior beyond that: output degrades gracefully when time is omitted (no rising sign or houses), the server performs place lookup, and the response includes external links and guide pages. It stops short of covering accuracy caveats or error cases.

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 compact sentences, front-loaded with the core capability and followed by conditional behavior, input conventions and return values. Every sentence carries information; there is no filler, though the time-conversion instruction slightly overlaps the schema.

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?

There is no output schema, and the description compensates by describing what comes back (placement details plus 3D sky link and guide pages) and how the result changes when birth time is missing. For a six-parameter open-world computation tool this is close to complete, with only minor gaps such as failure modes or place-resolution ambiguity.

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 every parameter including the house-system enum and optional coordinates. The description reinforces place handling ('pass as the person said it; the server looks it up') and time conversion, but it does not explain the latitude/longitude skip-search shortcut or the house_system choice, so it adds only modest value over 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 opens with a specific verb and resource ('Draw an accurate birth (natal) chart') and enumerates the exact outputs (Sun, Moon, rising sign, planets with sign/degree/house, angles, aspects). It is unambiguous what the tool produces, but it does not name or distinguish itself from the sibling tools famous_chart and sky_now, which keeps it from a 5.

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?

Usage is implied: call it when you have a birth date and optional time/place to compute a natal chart. It gives helpful input-handling guidance ('Works without a birth time', 'Pass the place as the person said it', 'Convert the time to 24-hour local time'), but it never states when to prefer this over famous_chart or sky_now, nor any exclusions.

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