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

Adds substantial context beyond the annotations: a concrete cost model (0.1 credit/call, billed per started block of 10, only successful calls charged, sandbox key free with fixed sample), an explicit determinism guarantee, and the sidereal/tropical output-shape difference. The read-only, idempotent and non-destructive profile is already carried by annotations, so this is genuinely additive rather than restated.

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 decision-relevant sentence, then payoff fields, cost, determinism and an example — each block is distinct and earns its place. The example arguments are mildly redundant given the 100%-covered schema, keeping it just short of ideal.

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, yet the description still summarizes the payload shape. With 5 parameters, enums, billing and precision caveats all covered, an agent has everything needed to call this correctly on the first attempt.

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 coverage is already 100% and includes defaults and enum caveats (MeanNode/TrueNode = Rāhu, Ketu = node+180), so the baseline is 3. The description still adds value by pairing the sidereal mode with the nakṣatra/pada output and by supplying a complete, valid example argument set that shows how datetime, bodies, zodiac and ayanamsa combine.

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 verb and resource ('where the Sun, Moon and planets are at a moment') and enumerates exactly what is returned (longitude, latitude, distance, speed, retrograde flag, sign, nakṣatra/pada when sidereal). It explicitly distinguishes itself from the reading-oriented siblings with 'not a reading', which is the key ambiguity in this tool set.

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 ... at a moment ... not a reading' gives a clear positive trigger and a negative boundary against the many reading/interpretation siblings. It does not, however, route among the close ephemeris siblings (get_ephemeris_series for time ranges, get_ephemeris_angles, get_ephemeris_ayanamsa, get_ephemeris_sunrise), so an agent must infer that this is the single-moment variant.

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