ephemeris_planet_position

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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds useful context: the credit cost (1 credit per call), the South Node workaround (no ID, opposite of North Node), and the specific output fields. It does not contradict annotations and provides extra information beyond safety flags.

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?

The description is well-organized: a clear main sentence, then structured supplementary sections (IDs, South Node, cost, example). It is front-loaded with the core purpose. Some redundancy exists because the planet ID list duplicates the schema, but the additional notes and example justify the length. It is not overly verbose for the information conveyed.

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?

Given the lack of an output schema, the description adequately lists the return fields (longitude, latitude, distance, speed, retrograde status). It also covers important edge cases (South Node) and cost. It does not explicitly state geocentric vs. topocentric behavior, but the optional observer coordinates in the schema imply this. Overall, it is sufficiently complete for a single-body ephemeris query.

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 parameters are already well-documented. The description repeats the planet_id list and adds a clarifying South Node note, but this info is also in the schema. The example maps parameters to values, but that's illustrative rather than adding new semantic meaning. The mention of output fields helps understand the purpose of parameters but does not deepen parameter-level understanding.

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 clearly states the tool 'gets' specific data (ecliptic longitude, latitude, distance, speed, retrograde status) for a 'single planet/body at a given date and time.' It sets it apart from sibling chart tools like ephemeris_natal_chart or ephemeris_transits by emphasizing the single-body, position-only scope. The planet ID enumeration further reinforces the resource being acted on.

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 rather than explicit. The description says 'for a single planet/body,' which suggests when to use this tool, but there is no direct comparison to alternatives like ephemeris_retrograde_status (which might focus on retrograde alone) or ephemeris_house_cusps. The example provides a concrete scenario, but no 'use this instead of X' or 'not for full charts' guidance is given.

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