Asterwise

Western Synastry

asterwise_get_western_synastry

Read-onlyIdempotent

Aspect grid between two natal charts using the tropical zodiac. Returns all inter-chart aspects using standard inter-chart orbs. Useful for relationship compatibility analysis.

WORKFLOW: BEFORE: asterwise_get_western_natal per person — understand charts individually first. AFTER: asterwise_get_western_composite — midpoint chart for the relationship itself.

INPUT CONTRACT: person1, person2 — each WesternBirthData (date, time, lat, lon, timezone). house_system ignored for synastry payload.

DO NOT CONFUSE WITH: asterwise_get_western_composite — one merged midpoint chart vs synastry (two charts overlaid). asterwise_get_western_compatibility — numeric 0–100 score vs raw aspects.

Full output and error contract: https://docs.asterwise.com/mcp/tools/get-western-synastry/

Input Schema

TableJSON Schema

Name	Required	Description	Default
`person1`	Yes	Birth data for Western astrology tools (tropical zodiac).
`person2`	Yes	Birth data for Western astrology tools (tropical zodiac).
`response_format`	No	Output format: 'markdown' (default) for a readable report, or 'json' for the raw structured payload.	markdown

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

Changed1 schema field changedSep 5, 2026

addedInput schema / properties / response_format / description

Added value: +"Output format: 'markdown' (default) for a readable report, or 'json' for the raw structured payload."

Changed2 schema fields changedSep 4, 2026

addedInput schema / properties / response_format / default
```
Added value: +"markdown"
```

changedInput schema / required

Previous value: -[
-  "person1",
-  "person2",
-  "response_format"
-]New value: +[
+  "person1",
+  "person2"
+]

AddedMay 1, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds meaningful behavioral context beyond the annotations: it uses the tropical zodiac, standard inter-chart orbs, and explicitly notes that house_system is ignored for the synastry payload. This is useful for avoiding a caller expectation that house systems affect the result.

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

Conciseness4/5

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

The description is longer than average but every labeled section earns its place: purpose, workflow, input contract, and sibling disambiguation. The structure makes it scannable, and the most important identifying information is front-loaded. It is not overly verbose, though the docs link could be considered optional.

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?

Given the tool's complexity, rich input schema, output schema presence, and full annotations, the description is complete enough. It covers prerequisites, follow-up workflow, input expectations, the ignored parameter gotcha, and distinguishes sibling tools. The agent has everything needed to invoke it correctly.

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

Parameters4/5

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

Schema description coverage is 100%, and the schema already documents each field, so the baseline is 3. The description adds extra value by stating that person1/person2 follow WesternBirthData format and by calling out that house_system is ignored for synastry payload, which prevents misusing a schema field. This pushes it above baseline.

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 states a specific deliverable: 'Aspect grid between two natal charts using the tropical zodiac' and 'Returns all inter-chart aspects using standard inter-chart orbs.' It also explicitly distinguishes itself from asterwise_get_western_composite and asterwise_get_western_compatibility, ensuring an agent can identify what this tool uniquely does.

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 WORKFLOW section explicitly tells the agent to call asterwise_get_western_natal per person before this tool and asterwise_get_western_composite after. The DO NOT CONFUSE WITH section names the two closest alternatives and explains the difference (one merged midpoint chart vs two charts overlaid; numeric score vs raw aspects), giving clear when-to-use guidance.

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

Disambiguation3/5

Many tools are well-differentiated by explicit 'DO NOT CONFUSE WITH' notes, but the sheer number of near-neighbor pairs (e.g., crystal vs gemstone recommendations, natal chart variants, dasha systems, compatibility systems, tarot draw variants) creates real selection risk. The descriptions mitigate overlap, but an agent browsing 103 tools will struggle to pick the right one.

Naming Consistency5/5

Every tool follows the asterwise_get_* or asterwise_draw_* prefix convention with a clear noun phrase (e.g., asterwise_get_natal_chart, asterwise_draw_tarot_cards). The two verbs 'get' and 'draw' are semantically appropriate, and there are no camelCase or mixed-style names.

Tool Count1/5

103 tools is far beyond a manageable MCP surface. While the domain is broad (Vedic astrology, Western astrology, numerology, tarot, crystals, dream symbols), the server bundles multiple distinct domains into one namespace, making it nearly impossible for an agent to discover the right tool efficiently.

Completeness4/5

The surface is impressively comprehensive across astrology, numerology, tarot, and remedies, with deep coverage of dasha systems, compatibility frameworks, and chart types. Minor gaps exist (e.g., no tarot interpretation endpoint, no batch operations, no update/delete since it's read-only data), but for a reference/prediction API the coverage is strong.

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