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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description adds material context the annotations cannot: cost model (0.1 credit/call, billed per 10-call block, only successful calls charged, free sandbox key with fixed sample) and determinism. That is exactly the kind of operational disclosure an agent needs before spending credits.

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?

Front-loaded with the when-to-use clause, then the precise geometric definition, cost, determinism, and an example. Well ordered and mostly tight; the billing sentence is the longest but earns its place for a paid tool.

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 not be re-described, and the description covers everything else an agent needs: when to call it, the exact astronomical convention, cost, determinism, and a sample invocation. Complete for a 4-param read-only computation.

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% and all four parameters carry their own descriptions (date format, IANA timezone, lat/long sign conventions), so the schema does the heavy lifting. The description's example arguments add a concrete usage pattern but no new constraint or syntax beyond 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?

Names a specific computation (sunrise, sunset, and next sunrise) for a given date and place, and precisely defines what 'sunrise' means here (upper limb at sea-level horizon with 36.6′ refraction). This distinguishes it from generic ephemeris siblings like get_ephemeris_positions or get_ephemeris_angles.

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?

'Use this when you need sunrise and sunset for a date and place, or where the Vedic day begins' gives clear triggering context, including the Vedic-day use case that motivates the tool. It stops short of naming which sibling to use instead when the agent wants angles or planetary positions, so no explicit exclusions.

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