MysticAPI

sky_personal

Render a personal natal sky as an SVG from a UTC birth instant: each body placed on the wheel, retrogrades marked, fixed stars conjunct natal points lit. Deterministic (same birth → same sky). Convert local birth time to UTC before calling. Returns SVG markup. Costs 1 call.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "year": "<year>",
      "month": "<month>",
      "day": "<day>",
      "hour": "<hour>",
      "minute": "<minute>"
    },
    "name": "sky_personal"
  }
}

Input Schema

Name	Required	Description
`day`	Yes
`hour`	Yes	Hour 0-23 in UTC
`year`	Yes	4-digit year (UTC)
`month`	Yes
`minute`	Yes
`second`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedJul 19, 2026
- changedInput schema / properties / hour / description
```
Previous value: -"Hour 0–23 in UTC"New value: +"Hour 0-23 in UTC"
```
First observedJul 7, 2026

TDQS

A4.2/5.0

Behavior4/5

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

With no annotations provided, the description carries full burden. Discloses determinism (same birth → same sky), output format (SVG markup), and cost. Describes what is rendered: bodies, retrogrades, conjunct fixed stars. Lacks details on authorization or rate limits, but sufficient for safe invocation.

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 sentences with no wasted words. First sentence front-loads the core purpose, output, and key features (retrogrades, fixed stars). Second sentence adds deterministic behavior, UTC requirement, and cost. Every sentence earns its place.

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?

For a tool with 6 parameters, no output schema, and no annotations, the description provides sufficient context: it explains what the tool does, what it includes, its determinism, and how to prepare input (UTC conversion). It does not detail the SVG structure or error handling, but overall is complete enough for an agent to use correctly.

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 only 33% (hour, year have descriptions). The description adds the crucial context that all parameters represent a UTC birth instant and reminds to convert local time. However, it does not explain individual parameters (e.g., day, month, minute) beyond what the schema already specifies. Adequate but not compensating fully for low coverage.

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 renders a personal natal sky as SVG from a UTC birth instant, specifying verb (render), resource (natal sky), and output format. Distinguishes from siblings like 'sky_today' by focusing on a specific birth moment vs current sky.

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

Usage Guidelines4/5

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

Provides explicit guidance to convert local birth time to UTC before calling, which is critical for correct usage. Includes cost info ('Costs 1 call'). Does not explicitly state when to avoid this tool or list alternatives among siblings, but the context is clear.

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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