Lounge Frog

Find cruise lines

list_cruise_lines

Read-onlyIdempotent

Cruise lines on Cruises Frog with their style, who they suit, fleet rating (the average of their ships' editorial scores), owner, ship count, solo cabins, and page link. Narrow by style, audience (e.g. families) or solo cabins and sort by rating to answer "best cruise line for ..." questions. For someone cruising alone, get_cruise_line has each line's single supplement and solo meetups, and https://cruisesfrog.com/solo-cruises compares them.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "list_cruise_lines"
  }
}

Input Schema

Name	Required	Description
`sort`	No	Default name
`style`	No
`region`	No	Only lines with ships sailing this region (slug or name, from list_cruise_regions)
`audience`	No	Only lines that list this audience
`solo_cabins`	No	Only lines with cabins built for one person: on every ship (fleetwide), on some ships, or either (any)

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 5, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare read-only, idempotent, closed-world behavior, so the bar is lower; the description still adds value by defining fleet rating as the average of ships' editorial scores and by listing the fields in each result, which matters because there is no output schema. It does not discuss result volume or pagination, which is the remaining gap.

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?

Front-loads the returned fields, then filters, then the routing alternative to get_cruise_line in three dense sentences with no filler. The closing solo-cruises comparison link is slightly promotional but still serves routing, so it earns most of its space.

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

Completeness5/5

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

With five optional filters, no output schema, and no required parameters, the description compensates by listing the returned attributes and defining the derived fleet rating field. Combined with the sibling routing note, an agent has everything needed to call this correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 80%, so most filter meaning is already structured. The description still adds intent beyond the schema — pairing "sort by rating" with the "best cruise line for ..." question type, and explaining the audience filter with a families example. The region filter, documented in the schema, is not echoed here, which is fine but leaves this short of a 5.

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?

Names the resource (cruise lines on Cruises Frog) and enumerates what each record carries: style, audience fit, fleet rating, owner, ship count, solo cabins, page link. It explicitly distinguishes itself from get_cruise_line, which is the per-line detail tool, so an agent can pick between them without opening a 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?

Gives concrete use conditions: narrow by style, audience, or solo cabins and sort by rating when answering "best cruise line for ..." questions. It also names the alternative (get_cruise_line) and the exact condition that selects it — solo supplement and meetup details for someone cruising alone.

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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