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egov-law-mcp

by SHAYOUWORLD
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@codeagentjp/egov-law-mcp

Servidor MCP stdio local para buscar leyes japonesas y recuperar el texto de artículos de e-Gov Law Search.

Este servidor no llama a un LLM. Solo devuelve datos legales respaldados por la fuente y URLs de e-Gov para que tu cliente MCP (Claude Desktop, Claude Code, Cursor o cualquier otro agente) pueda citar la fuente original.

Las decisiones de diseño se basaron en la lectura del proyecto de código abierto de la Agencia Digital Lawsy-Custom-BQ (publicado el 24-04-2026 como parte del lanzamiento de OSS de IA gubernamental Gennai). Consulta las notas de diseño en codeagent.jp.

Por qué otro e-Gov MCP

Existe un egov-law-mcp en npm de otro autor. Este paquete difiere en tres aspectos:

  1. find_related_laws — busca órdenes de ejecución (施行令) y reglamentos (施行規則) para un nombre de ley base dado. Lawsy-Custom-BQ tiene el mismo paso en el lado del servidor; útil porque las definiciones y las reglas delegadas a menudo residen fuera de la ley principal.

  2. Atribución de fuente integrada en cada resultado de herramienta — cada respuesta incluye el nombre de la ley, el ID de la ley, el número de artículo y la URL canónica de e-Gov, para que el LLM que realiza la llamada no pueda omitir la cita.

  3. .mjs de un solo archivo, sin paso de compilación — bin/egov-law-mcp.mjs se ejecuta directamente en Node 20+. Más fácil de auditar, instalación más pequeña.

Related MCP server: Houki e-Gov MCP Server

Estado

MVP. La superficie de la API es intencionalmente pequeña:

  • search_laws — busca leyes japonesas actuales por palabra clave.

  • get_article — recupera un artículo específico de una ley por ID de ley o número de ley.

  • get_law — recupera metadatos básicos y una vista previa del texto de una ley.

  • find_related_laws — encuentra leyes probablemente relacionadas con órdenes de ejecución y reglamentos.

Requisitos

  • Node.js 20 o posterior

  • Acceso a la red a https://laws.e-gov.go.jp

Instalación

Desde npm:

{
  "mcpServers": {
    "egov-law": {
      "command": "npx",
      "args": ["-y", "@codeagentjp/egov-law-mcp"]
    }
  }
}

Desde el código fuente para desarrollo:

git clone https://github.com/SHAYOUWORLD/egov-law-mcp.git
cd egov-law-mcp
node bin/egov-law-mcp.mjs
{
  "mcpServers": {
    "egov-law": {
      "command": "node",
      "args": ["/absolute/path/to/egov-law-mcp/bin/egov-law-mcp.mjs"]
    }
  }
}

Herramientas

search_laws

Busca en la lista de leyes de e-Gov.

{
  "keyword": "個人情報",
  "limit": 10
}

get_article

Recupera el texto del artículo. Proporciona lawId o lawNum.

{
  "lawId": "503AC0000000035",
  "article": "2"
}

get_law

Recupera metadatos básicos y una vista previa en texto plano de una ley.

{
  "lawId": "503AC0000000035",
  "previewChars": 3000
}

find_related_laws

Busca leyes cuyos nombres parecen estar relacionados con un nombre de ley base, incluidas órdenes de ejecución y reglamentos.

{
  "lawName": "個人情報の保護に関する法律",
  "limit": 10
}

Fuente de datos y atribución

Este paquete utiliza la API de e-Gov Law Search:

Los resultados de las herramientas incluyen atribución de fuente. Cuando publiques o redistribuyas resultados basados en este paquete, incluye una atribución de fuente de e-Gov adecuada.

Atribución sugerida:

出典: e-Gov法令検索（https://laws.e-gov.go.jp/）

Notas de seguridad

  • Este paquete es una herramienta de referencia legal, no asesoramiento legal. Verifica las conclusiones legales importantes con la página oficial de e-Gov y, cuando sea necesario, consulta a un profesional cualificado.

  • No ejecuta comandos de shell.

  • Solo escribe mensajes JSON-RPC en stdout y registra solo en stderr.

  • Solo obtiene endpoints de e-Gov Law Search.

Relacionado

Licencia

MIT © codeagent.jp

Available Tools

4 tools
get_articleB

Retrieve a specific article from e-Gov Law Search by law ID or law number.

ParametersJSON Schema
NameRequiredDescriptionDefault
lawIdNoe-Gov law ID, for example 503AC0000000035.
lawNumNoJapanese law number. Either lawId or lawNum is required.
articleYesArticle number, for example 2.
paragraphNoOptional paragraph number.

TDQS

B3.3/5.0
Behavior2/5

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

No annotations are provided, and the description only states 'retrieve' without disclosing behavioral traits such as idempotency, authentication needs, rate limits, or error handling for missing articles.

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 a single, concise sentence that front-loads the core purpose. However, it may be too brief for a tool with four parameters, missing important details about parameter dependencies.

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

Completeness2/5

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

For a tool with four parameters and no output schema or annotations, the description omits crucial context: it does not mention that the 'article' parameter is required, nor does it explain what the return value contains or how errors are handled.

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 the baseline is 3. The description's mention of 'by law ID or law number' adds minimal value beyond the existing schema descriptions, which already specify parameter purposes and constraints.

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 action (retrieve), resource (a specific article from e-Gov Law Search), and method (by law ID or law number). It distinguishes from sibling tools like get_law and search_laws by targeting articles specifically.

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 implies usage context (retrieving a specific article) but provides no explicit when-to-use or when-not-to-use guidance, nor does it reference alternatives among sibling tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

get_lawA

Retrieve law metadata and a plain text preview from e-Gov Law Search.

ParametersJSON Schema
NameRequiredDescriptionDefault
lawIdNoe-Gov law ID. Either lawId or lawNum is required.
lawNumNoJapanese law number. Either lawId or lawNum is required.
previewCharsNoMaximum preview length. Defaults to 5000.

TDQS

A3.5/5.0
Behavior3/5

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

No annotations provided; description implies a read operation but doesn't explicitly confirm idempotency, authentication needs, or rate limits. It only states what is retrieved, which is adequate but not exhaustive.

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?

Single sentence, clear, no unnecessary words. Front-loads the key action and resource.

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

Completeness3/5

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

Given 3 parameters, no output schema, and no annotations, the description is brief but covers the essential purpose. However, it lacks details about return format or side effects, which could be useful for a tool with no output schema.

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 covers 100% of parameters with descriptions. The description adds no extra meaning beyond the schema (e.g., 'metdata and preview' is generic). Baseline score of 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?

Description clearly states it retrieves law metadata and plain text preview from e-Gov. It specifies the source and distinguishes from sibling tools like search_laws (search) and get_article (specific article).

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

Usage Guidelines2/5

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

No guidance on when to use this tool versus siblings, nor any prerequisites (e.g., need a law ID from search_laws). The description is silent on usage context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

search_lawsB

Search current Japanese laws from e-Gov Law Search by keyword.

ParametersJSON Schema
NameRequiredDescriptionDefault
keywordYesKeyword to search in law name, law number, or law ID.
categoryNoLaw category. Defaults to all.
limitNoMaximum number of results. Defaults to 10.

TDQS

B3.4/5.0
Behavior2/5

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

No annotations are present, so the description must disclose behavioral traits. It only mentions 'current' laws, but lacks details on authorization, rate limits, data freshness, or any side effects. The bare statement is insufficient for a search tool.

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?

A single concise sentence with no superfluous words. It front-loads the action and resource, perfect for quick comprehension.

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

Completeness2/5

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

With no output schema and only three parameters, the description fails to explain return format, pagination, or result structure. Given the tool's complexity (search across categories), completeness is lacking.

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%, and the description adds no extra meaning beyond the schema. The search logic (e.g., partial matching, case sensitivity) is not explained, meeting the baseline for high 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?

The description clearly states the verb 'search', the resource 'current Japanese laws', and the source 'e-Gov Law Search by keyword', distinguishing it from siblings like find_related_laws and get_article which target specific relations or articles.

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 implies general keyword search but does not explicitly state when to use this tool versus alternatives, nor does it mention when not to use it. No exclusions or prerequisites are provided.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 4 tool updatesv0.1.0
    • First observedfind_related_laws
    • First observedget_article
    • First observedget_law
    • First observedsearch_laws
Deploy Server
One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

TDQS

A3.8/5.0

Scored across 4 tools

Disambiguation5/5

Each tool has a distinct purpose: searching laws, retrieving law metadata, retrieving specific articles, and finding related laws. No overlap in functionality.

Naming Consistency5/5

All tool names follow a consistent verb_noun pattern in snake_case, e.g., search_laws, get_law, get_article, find_related_laws.

Tool Count5/5

With 4 tools, the server is well-scoped for a focused legal search assistant. The count is neither excessive nor insufficient.

Completeness4/5

The tool set covers the core operations for searching and retrieving Japanese laws and articles. A minor gap is the lack of a tool to list all laws, but for search purposes this is acceptable.

Maintenance

ActivityMaintained
ResponsivenessUnresponsive

Resources

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