1820.ch – Telefonbuch Schweiz

Browse a business category

browse_business_category

Read-onlyIdempotent

Lists public directory entries in one business category, optionally narrowed to a locality/postcode/canton. Use search_swiss_directory instead for a free-text query.

Input Schema

TableJSON Schema

Name	Required	Description
`lang`	No	Response language: de, fr, it, or en. Defaults to de.
`limit`	No	Maximum number of results, 1-20.
`category`	Yes	The business category slug (e.g. "restaurant", "coiffeur", "sanitaer"). Valid slugs are the slug values in categories, as returned by get_directory_entry, or a top-level group slug such as "bau-handwerk".
`location`	No	Locality, postcode, or canton (e.g. "Baden", "5400", "ZH") to narrow the category to. Always put a place name here.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`source`	Yes
`results`	Yes
`retrieved_at`	Yes
`advertising_block_note`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedSep 27, 2026

addedInput schema / properties / category / maxLength
```
Added value: +200
```

addedInput schema / properties / lang

Added value: +{
+  "description": "Response language: de, fr, it, or en. Defaults to de.",
+  "enum": [
+    "de",
+    "fr",
+    "it",
+    "en"
+  ],
+  "type": "string"
+}

changedInput schema / properties / location / description

Previous value: -"Optional locality, postcode, or canton name to narrow the category to."New value: +"Locality, postcode, or canton (e.g. \"Baden\", \"5400\", \"ZH\") to narrow the category to. Always put a place name here."

addedInput schema / properties / location / maxLength
```
Added value: +200
```

First observedSep 27, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description still adds useful context by specifying that results are public directory entries and that narrowing is optional rather than required. It does not discuss pagination or result ordering, but with annotations and a 1-20 limit in the schema the remaining gap is small.

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, zero filler, and the core behavior plus scope constraint is front-loaded before the sibling routing advice. Every clause carries information an agent needs.

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?

With full schema coverage, annotations, and an output schema present, the description need not explain return values or formats. It covers purpose, scoping, and the alternative route, leaving only minor edge cases (e.g., invalid slug handling) unaddressed.

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 schema already documents category slugs, lang, limit, and location formats. The description adds only a light reinforcement of the optional location narrowing, so it does not meaningfully exceed what the schema provides.

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?

States a specific verb and resource ('Lists public directory entries in one business category') plus the precise scope narrowing (locality/postcode/canton). It also explicitly names the sibling it is not, so an agent can distinguish it from search_swiss_directory without reading either schema.

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 description gives an explicit routing rule: use this tool for category browsing and 'use search_swiss_directory instead for a free-text query.' That is a clear when-to-use-this vs. when-to-use-the-alternative statement, with the selecting condition named.

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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