Deterministic Korean Saju / Chinese BaZi Four Pillars MCP server. Heavenly Stems, Earthly Branches, Day Master, five-element distribution, and 0-100 compatibility. No AI, no API key.
Scored across 2 tools
The two tools have clearly distinct purposes: bazi_chart computes a single person's chart, while bazi_compatibility evaluates compatibility between two people. No overlap in functionality.
Both tools follow a consistent 'bazi_' prefix with underscore-separated descriptive nouns (chart, compatibility), forming a clear and predictable naming pattern.
With only 2 tools, the server feels slightly thin for a full 'Four Pillars' server, though it covers core chart computation and compatibility. A typical server of this scope might include 3-5 tools.
The server lacks tools for interpreting the chart, analyzing element relationships, or providing detailed profiles beyond the raw chart and a compatibility score. This leaves significant gaps in the expected lifecycle.
Compute a deterministic BaZi (八字) / Korean Saju (사주) Four Pillars chart from a solar birth date: Heavenly Stems, Earthly Branches, Day Master, and five-element distribution. KASI-validated engine, no AI.
| Name | Required | Description | Default |
|---|---|---|---|
| day | Yes | ||
| hour | No | 0–23, or -1 if birth time unknown | |
| year | Yes | 1920–2050 | |
| month | Yes | ||
| gender | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so description carries full burden. It states the tool is 'deterministic' and 'KASI-validated', giving some insight into computation reliability. However, it does not disclose potential error conditions, authentication needs, or side effects. For a compute-only tool, 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.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single concise sentence that immediately states the purpose and outputs. It is front-loaded with the key action. No unnecessary words, making it efficient for an agent to parse.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool has no output schema, the description adequately lists the chart components (Stems, Branches, Day Master, distribution). It covers what the agent needs to know about the result. Missing error handling or edge cases, but for a compute tool this is reasonably complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is only 40%, meaning most parameters (day, month, gender) lack description. The tool description does not add meaning beyond listing the chart components. It does not explain how parameters like 'gender' or 'hour' influence the output, leaving ambiguity for the agent.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Description clearly states the tool computes a deterministic BaZi/Saju chart from solar birth date, listing outputs (Heavenly Stems, Earthly Branches, Day Master, five-element distribution). The name and description distinguish it from the sibling tool 'bazi_compatibility' by focusing on single chart computation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description mentions 'KASI-validated engine, no AI' implying reliability but does not explicitly state when to use this tool versus the sibling 'bazi_compatibility'. There is no guidance on prerequisites or when not to use. The context of a single sibling suggests the alternative is for compatibility, but it's not stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Deterministic BaZi compatibility score (0–100) and band between two people, from combined five-element balance and Day Master cycle relation.
| Name | Required | Description | Default |
|---|---|---|---|
| person_a | Yes | {year,month,day,hour,gender} | |
| person_b | Yes | {year,month,day,hour,gender} |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden. It states the tool is 'Deterministic', implying no randomness, and explains the underlying logic. However, it does not disclose any side effects, authentication needs, or rate limits. For a computation tool, this is acceptable 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.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence that conveys the core functionality and output. It is front-loaded with the key information and contains no fluff.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
The description explains the output format (score and band) and the method, which is helpful without an output schema. However, it does not elaborate on input constraints (e.g., valid date ranges) or handle nested object complexity. Overall, it provides adequate but not exhaustive context.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100% because each property has a description, but those descriptions are minimal (just field names). The main description adds context about comparing 'two people'. Baseline 3 is appropriate as the schema covers the structure, but the description does not significantly enhance understanding of parameter formats.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool calculates a 'Deterministic BaZi compatibility score (0–100) and band' using specific methods ('five-element balance and Day Master cycle relation'). It distinguishes from the sibling tool bazi_chart by focusing on compatibility rather than chart generation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus bazi_chart or any other alternatives. The description implies use for comparing two people but does not specify prerequisites or scenarios where it should be avoided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
bazi_chartbazi_compatibility
Add one secure layer between your agents and this server.