vessel-traffic-mcp

Vessel Position

vessel_position

Read-onlyIdempotent

Retrieve the latest known vessel position by MMSI or IMO, including source, observation time, and freshness metadata.

Instructions

Return the latest known position for a vessel by MMSI or IMO with source, retrievedAt, observedAt, and freshness metadata.

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": "vessel_position"
  }
}

Input Schema

Name	Required	Description	Default
`mmsi`	No
`imo`	No
`provider`	No
`credentialProfile`	No
`oneTimeCredential`	No
`fallbackPolicy`	No
`coverageHint`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0May 27, 2026

TDQS

A3.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and idempotentHint=true, and the description adds value by specifying that the return includes source, retrievedAt, observedAt, and freshness metadata. No contradiction with 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?

The description is a single, front-loaded sentence with no filler. Every word contributes to understanding the tool's purpose.

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

Completeness2/5

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

Given the complexity of 7 parameters including authentication/providers and no output schema, the description falls short. It does not address authentication requirements, credential handling, or fallback policies, which are crucial for execution.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must add meaning beyond parameter names. It only clarifies MMSI/IMO but omits explanations for provider, credentialProfile, oneTimeCredential, fallbackPolicy, and coverageHint, leaving most parameters semantically under-explained.

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?

The description clearly states 'Return the latest known position for a vessel by MMSI or IMO' using a specific verb and resource, and distinguishes from sibling tools like vessel_track (historical) and vessel_search (finding vessels).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No explicit guidance on when to use this tool versus alternatives such as vessel_track for historical data or vessel_area for area-based queries. The description implies it's for the latest position but lacks when-not-to-use guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server