Maritime Vessel Data MCP Server

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list_regions

Identify sea areas you can monitor and their measured message rates, helping you choose regions that fit your subscription budget.

Instructions

List the sea areas this server can watch, and what each one costs.

The feed is rationed by throughput rather than by area. A subscription above roughly 25 messages a second is closed by the vendor within a couple of minutes, and a whole-world subscription dies inside one, so a selection has to be chosen to fit a budget rather than simply widened.

Each region reports its measured message rate. A rate of null means nobody has measured that region yet, and a selection containing one has an unknown total: that is reported as unknown rather than as a partial sum. Use set_regions to change what is being watched.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 21, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Despite no annotations, the description discloses throughput rationing, vendor-enforced subscription limits (25 msg/s, whole-world dies within a minute), null rate semantics, and unknown total reporting behavior. This fully compensates for the missing annotations.

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?

Front-loaded with the purpose, then logically flows through budget constraints, rate reporting, null behavior, and the sibling tool for changes. Every sentence adds operational value without padding.

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?

Covers purpose, cost structure, rate limits, null/unknown handling, and how to change regions. With an output schema present, no return-format details are missing. Complete for an agent to call 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?

The tool has zero parameters, so the description correctly focuses on output semantics (rates, costs, null handling). Baseline for 0 params is 4, and the description adds value by explaining the meaning of the returned data.

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 action ('List') and resource ('sea areas this server can watch') plus what each one costs. This clearly distinguishes it from siblings like set_regions (change) and vessels_in_area (vessel querying).

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?

Provides operational context on throughput limits and explicitly directs to set_regions for changing the watched set, making the tool's role evident. It implies when to use this tool: to pick a budget-compliant selection of areas.

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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