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caelus-mcp

by io.github.heavyblotto

synastry

Compare two people's birth charts: inter-chart aspects with orbs, house overlays both ways, plus ranked citable fact atoms and a ready brief (synastry/composite ids for auditCitations). Each person needs date+lat+lon. House overlays always use Placidus (not configurable here).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
aYesPerson A birth data (UTC date, lat, lon)
bYesPerson B birth data (UTC date, lat, lon)
orbNoMax orb in degrees
zodiacNotropical (default) or sidereal:<ayanamsa>tropical

TDQS

A3.8/5.0
Behavior3/5

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

The description discloses that house overlays always use Placidus (non-configurable). However, it does not mention whether the tool is read-only, permission requirements, or rate limits. With no annotations, this is adequate but not comprehensive.

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?

Three sentences, front-loaded with purpose, no wasted words. Each sentence adds value: purpose/output, prerequisites, behavioral constraint.

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?

Given the complexity of synastry (multiple outputs, 4 parameters, no output schema), the description covers the key aspects: what is produced (aspects, overlays, fact atoms, brief) and a constraint (Placidus). Missing details on 'fact atoms' and output structure, but sufficient for an agent to understand.

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%, so baseline is 3. The description reiterates prerequisites already in schema (date, lat, lon) but adds no new meaning beyond what the schema provides. The fixed house system note is behavioral, not parameter-specific.

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 clearly states the verb 'compare two people's birth charts' and specifies the outputs: inter-chart aspects, house overlays, ranked fact atoms, and a brief with IDs. This distinguishes it from sibling tools like 'composite' which combines charts into one.

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 mentions prerequisites (date+lat+lon for each person) but does not explicitly state when to use this tool versus alternatives like 'composite' or 'aspect_patterns'. Usage guidance is implied rather than explicit.

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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TDQS

A3.9/5.0
Disambiguation5/5

Each tool has a highly specific and well-described purpose. Despite the large number, their functions are clearly distinct—e.g., natal_chart vs current_sky vs composite, or dasha vs firdaria vs profections vs releasing. The detailed descriptions prevent ambiguity.

Naming Consistency3/5

Names are consistently in snake_case but vary in style: some are noun phrases (natal_chart, cosmic_weather), some are verb-like (releasing, returns), and some are descriptive (aspect_patterns, find_aspect_dates). There is no strict verb_noun pattern, leading to moderate consistency.

Tool Count4/5

34 tools is high but appropriate for a comprehensive astrology API covering natal, transits, progressions, returns, synastry, time-lord techniques, sky events, and synthetic bodies. Each tool serves a specific niche, so the count feels justified rather than excessive.

Completeness5/5

The tool surface is extremely thorough, covering all major areas of astrology: chart generation, aspects, configurations, dignities, time-lord techniques (multiple systems), synastry, composite, progressions, returns, transits, sky events, rectification, electional, and synthetic bodies. No obvious gaps for the intended domain.

Resources