Lex: Luxembourg Law MCP Server

diff

What changed between two dates for one work: which publisher versions cover the selected dates and, where both texts are held, retrieve them via as_of to compare. An optional held article anchor scopes the typed comparison workspace. Read timeline_semantics before describing legal applicability.

Input Schema

TableJSON Schema

Name	Required	Description
`work`	Yes	Work-level lex_id (publisher:workkey), version-level lex_id (version segment ignored), or verbatim publisher identifier with publisher supplied. Unknown document -> call search first.
`anchor`	No	optional held provision anchor returned by search, e.g. art_92
`to_date`	Yes	ISO date
`language`	No	language code
`from_date`	Yes	ISO date
`publisher`	No	publisher id; required when work is not publisher-qualified
`to_version_key`	No	optional opaque key returned by timeline or an ambiguous_version choice
`from_version_key`	No	optional opaque key returned by timeline or an ambiguous_version choice

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedAug 17, 2026

changedInput schema / properties / from_date / pattern

Previous value: -"^[0-9]{4}-[0-9]{2}-[0-9]{2}$"New value: +"^\\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$"

addedInput schema / properties / from_version_key

Added value: +{
+  "description": "optional opaque key returned by timeline or an ambiguous_version choice",
+  "maxLength": 128,
+  "minLength": 1,
+  "type": "string"
+}

changedInput schema / properties / to_date / pattern

Previous value: -"^[0-9]{4}-[0-9]{2}-[0-9]{2}$"New value: +"^\\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$"

addedInput schema / properties / to_version_key

Added value: +{
+  "description": "optional opaque key returned by timeline or an ambiguous_version choice",
+  "maxLength": 128,
+  "minLength": 1,
+  "type": "string"
+}

Changed15 schema fields changedAug 11, 2026

addedInput schema / additionalProperties
```
Added value: +false
```
addedInput schema / properties / anchor / maxLength
```
Added value: +512
```
addedInput schema / properties / anchor / minLength
```
Added value: +1
```
addedInput schema / properties / from_date / maxLength
```
Added value: +10
```
addedInput schema / properties / from_date / minLength
```
Added value: +1
```
addedInput schema / properties / from_date / pattern
```
Added value: +"^[0-9]{4}-[0-9]{2}-[0-9]{2}$"
```
addedInput schema / properties / language / maxLength
```
Added value: +16
```
addedInput schema / properties / language / minLength
```
Added value: +1
```

addedInput schema / properties / publisher

Added value: +{
+  "description": "publisher id; required when work is not publisher-qualified",
+  "maxLength": 64,
+  "minLength": 1,
+  "type": "string"
+}

addedInput schema / properties / to_date / maxLength
```
Added value: +10
```
addedInput schema / properties / to_date / minLength
```
Added value: +1
```
addedInput schema / properties / to_date / pattern
```
Added value: +"^[0-9]{4}-[0-9]{2}-[0-9]{2}$"
```

changedInput schema / properties / work / description

Previous value: -"Work-level lex_id (publisher:workkey), version-level lex_id (version segment ignored), or verbatim publisher identifier. Unknown document -> call search first."New value: +"Work-level lex_id (publisher:workkey), version-level lex_id (version segment ignored), or verbatim publisher identifier with publisher supplied. Unknown document -> call search first."

addedInput schema / properties / work / maxLength
```
Added value: +1000
```
addedInput schema / properties / work / minLength
```
Added value: +1
```

Changed1 schema field changedAug 9, 2026

addedInput schema / properties / anchor

Added value: +{
+  "description": "optional held provision anchor returned by search, e.g. art_92",
+  "type": "string"
+}

First observedAug 5, 2026

TDQS

B3.4/5.0

Behavior3/5

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

With no annotations, the description carries the full burden. It discloses that the tool retrieves texts 'via as_of' and that an anchor 'scopes the typed comparison workspace,' which adds some behavioral context. However, it does not state whether this is a read-only operation, describe side effects, or explain behavior when texts are not held or no versions match.

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 two sentences and front-loads the core purpose. The second sentence is dense, incorporating references to as_of and timeline_semantics, but there is no filler. It earns a 4 rather than 5 due to the slightly convoluted phrasing of the second sentence.

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?

The tool has 8 parameters, no output schema, and no annotations, so the description must carry significant weight. It gives a solid overview of the diff operation and mentions prerequisites, but it does not cover parameter relationships (e.g., when publisher is required) or edge cases (e.g., no versions found). It also does not sufficiently differentiate from the sibling 'changes_in_period.'

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 adds minor semantic context by referring to the 'anchor' as a 'held article anchor' and mentioning 'typed comparison workspace,' but it does not provide meaningful additional meaning for most parameters (e.g., to_version_key, from_version_key, language) beyond what the schema already includes.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'What changed between two dates for one work' and explains that it identifies publisher versions covering the dates and retrieves them via as_of for comparison. This is a specific verb+resource. However, it does not explicitly distinguish the tool from the similar sibling 'changes_in_period', so it falls short of a perfect 5.

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 when comparing two dates for a single work, and includes a crucial instruction: 'Read timeline_semantics before describing legal applicability.' However, it does not explicitly state when to use this tool versus alternatives like as_of or changes_in_period, nor does it provide exclusion criteria. Guidance is only implied.

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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