Maritime Vessel Data MCP Server

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vessels_near_port

Lists vessels within a radius of a named Malaysian port, returning nearest first with distance. Shows match/return counts and flags stale snapshot data.

Instructions

List vessels within a radius (nautical miles) of a named port.

Recognized ports: Port Klang, Tanjung Pelepas, Penang, Malacca, Langkawi. Returns JSON with a "data" block stating the source, a "matches" count of everything inside the radius, a "returned" count of how many are included, and a "vessels" list annotated with distance_nm, nearest first. When returned is less than matches the nearest were kept and the rest omitted. When data.source is "snapshot" the positions are not current: say so when answering.

Input Schema

TableJSON Schema

Name	Required	Description
`port`	Yes	Port name. One of: Port Klang, Tanjung Pelepas, Penang, Malacca, Langkawi. Case insensitive.
`limit`	No	Maximum number of vessels to return, nearest first, between 1 and 200. The response always reports how many matched, so a truncated answer is visible rather than silent.
`radius_nm`	No	Search radius in nautical miles, greater than 0 and at most 500. The server only receives traffic for Malaysian waters, so a radius beyond that covers sea it never sees.

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

A3.8/5.0

Behavior4/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly explains the response structure, the meaning of matches vs. returned, the truncation behavior (nearest kept), and the important caveat that a data.source of 'snapshot' means positions are not current. This is valuable beyond the schema, though it does not cover permissions, rate limits, or side effects.

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?

The description is front-loaded with the core purpose, followed by concise but essential details: recognized ports, response structure, truncation behavior, and the snapshot caveat. Every sentence earns its place and there is no redundant filler.

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?

Given the rich input schema and its own explanation of the output, the description is nearly complete for correct invocation. It covers recognized ports, response fields, truncation, and the snapshot caveat. The main gap is lack of explicit sibling differentiation, but the tool can still be used correctly without it.

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%, and the parameter descriptions in the schema are already rich (e.g., limit communicates truncation visibility, radius_nm notes Malaysian waters coverage). The tool description adds little parameter-specific meaning beyond what the schema already provides, so the baseline of 3 is appropriate.

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 opens with a specific verb and resource: 'List vessels within a radius (nautical miles) of a named port,' and enumerates the recognized ports. This clearly states the tool's function, though it does not explicitly contrast it with sibling tools like vessels_in_area or search_vessels.

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 usage context is implied by the verb 'List' and the port/radius parameters, and the recognized ports are enumerated. However, there is no explicit guidance on when to prefer this tool over sibling tools such as vessels_in_area or search_vessels, and no exclusion criteria are given.

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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