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explore_natal_chart

Read-onlyIdempotent

Renders an interactive birth-chart wheel for natal requests; click any planet, house, or aspect for instant interpretation. Supports house-system switching.

Instructions

PRIMARY tool for any natal/birth-chart request. Renders an interactive, clickable chart wheel — prefer this over ephemeris_natal_chart when the user wants to SEE a chart. Returns an embedded visual chart explorer that lets you click any planet, house, or aspect line for instant astrological interpretation.

CREDIT COST: 1 credit per call.

Supports house system switching (Placidus, Whole Sign, Equal, Koch). The chart is computed using NASA JPL DE440 ephemerides for sub-arcsecond precision. Renders interactively in MCP Apps-capable hosts (Claude Desktop) and falls back to static SVG in other hosts.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
bodiesNoOptional list of body names to include. Defaults to 13 classical bodies (Sun through Pluto + Chiron + Nodes). Use 'all' as a single item to include every available body (Lilith, Ceres, Juno, Vesta, Pallas, Vertex, etc.). Example: ['sun','moon','lilith','vertex'].
datetimeYesISO 8601 datetime; zone required — a `Z`/±HH:MM suffix or the `timezone` argument. Date-only resolves to 12:00 UTC. Full rule: server `instructions`.
latitudeNoBirth latitude in decimal degrees (positive = North). Optional if `location` is a place name — the resolver fills it in. If you supply lat/lon directly, resolve them with location_search first; never recall coordinates from memory.
locationNoBirth location. Prefer a plain place name like 'New York, NY' — the server resolves it via the same lookup `location_search` uses (unambiguous names → coords + timezone; ambiguous names throw with a disambiguation hint). If you already have coords, either omit this or use it as a display caption; supplied coords always win.
timezoneNoIANA timezone (e.g. `America/Chicago`); required when the datetime is naive, ignored otherwise.
longitudeNoBirth longitude in decimal degrees (positive = East). Optional if `location` is a place name.
house_systemNoHouse system to use (default: placidus).
Behavior5/5

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

The description adds substantial behavioral context beyond annotations: credit cost, house system switching, NASA JPL DE440 ephemerides precision, and rendering behavior in different hosts (interactive vs static SVG). These details enrich the agent's understanding without contradicting the read-only and idempotent hints.

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?

The description is concise and well-structured, opening with the primary purpose and then providing differentiators, cost, and technical details. Every sentence earns its place with no redundant fluff.

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

Completeness5/5

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

For a visual chart tool with no output schema, the description adequately explains what is returned (interactive chart explorer, clickable elements) and how it behaves in different hosts. Combined with rich schema descriptions and annotations, the agent has complete information to select and invoke the tool.

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 coverage is 100% with detailed parameter descriptions (e.g., datetime timezone rules, location resolution). The description adds only marginal parameter context, such as mentioning house system switching. Since the schema already documents all parameters thoroughly, baseline 3 is appropriate.

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?

The description explicitly states it is the PRIMARY tool for natal/birth-chart requests and renders an interactive chart wheel. It also distinguishes itself from sibling ephemeris_natal_chart by stating 'prefer this over ephemeris_natal_chart when the user wants to SEE a chart.' This gives a specific verb, resource, and clear differentiation.

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

Usage Guidelines5/5

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

The description provides explicit when-to-use guidance: 'prefer this over ephemeris_natal_chart when the user wants to SEE a chart.' It also mentions host fallback behavior and names an alternative tool. This clearly signals when to use this tool versus the alternative.

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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