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ducrouxolivier

Swiss Ephemeris MCP Server

calculate_transits

Compare natal chart positions with current planetary transits by providing birth date, time, and location. Returns both birth chart and current positions for transit analysis.

Instructions

Calculate birth chart positions and current transits for comparison. Returns both natal chart and current planetary positions.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
birth_datetimeYesBirth datetime in ISO8601 format, e.g., 1985-04-12T23:20:50Z
latitudeYesBirth latitude in decimal degrees
longitudeYesBirth longitude in decimal degrees, positive east
Behavior2/5

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

No annotations are provided, so the description carries full burden. It states the tool calculates and returns positions, but gives no insight into behavior such as required authentication, rate limits, error handling for invalid coordinates, or the format of the return data.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two concise sentences with no wasted words. The key information is front-loaded: purpose and return value are immediately clear.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite no output schema, the description adequately explains that both natal and current planetary positions are returned. For a tool with 3 parameters and moderate complexity, this is nearly complete; however, it could benefit from mentioning the scope of planets or aspects included.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%: birth_datetime, latitude, and longitude are all clearly described in the schema. The tool description adds no additional parameter context beyond what is already provided by the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Description clearly states the tool calculates birth chart positions and current transits for comparison, and returns both natal chart and current planetary positions. This distinguishes it from siblings like calculate_planetary_positions (likely just positions) and calculate_synastry (comparison between two people).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage when comparing natal and transit positions, but does not explicitly state when to use this tool versus alternatives like calculate_planetary_positions or calculate_solar_revolution. No exclusions or prerequisites are mentioned.

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

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