Gangway AIS

Vessel now

get_vessel

Read-onlyIdempotent

One vessel now: her last position, speed, course, heading and navigational status from a source we may pass on, with her particulars (name, IMO, call sign, type, size, flag) and voyage (destination, ETA, draught). Give her MMSI, or her IMO number (then she is found by search first, 1 credit more). Credits: 1. Free accounts too: their answers are 24 hours behind, with a box of at most 1 square degree and 1,000 credits a month; paid plans are live.

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": "get_vessel"
  }
}

Input Schema

Name	Required	Description	Default
`imo`	No	The vessel's IMO number, seven digits
`mmsi`	No	The vessel's MMSI, nine digits

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 14, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Beyond the supplied readOnly/openWorld annotations it discloses cost (1 credit, +1 for IMO lookup) and a major data-quality caveat: free accounts return answers 24 hours behind, limited to a 1-square-degree box and 1,000 credits a month, while paid plans are live. It also flags that only sources that may be passed on are used, which an agent needs to know before relying on the data.

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?

Value-dense and front-loaded: the returned fields come first, then identification, then cost and tier caveats. The prose is a bit compressed into run-on clauses, but almost every clause carries actionable information.

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 no output schema, the description carries the return-value burden and does so by listing the position, particulars and voyage fields; it also covers cost and freshness. The remaining gap is behavior when both optional parameters are omitted and what errors look like.

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 100%, so format details are already covered; the description adds real meaning by explaining the consequence of choosing IMO over MMSI (an extra search step and 1 additional credit). It does not state what happens when neither optional identifier is supplied.

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 ('One vessel now') and enumerates exactly what is returned: last position, speed, course, heading, navigational status, particulars and voyage. The word 'now' implicitly separates it from history-oriented siblings such as vessel_track, so an agent can pick it without opening the schema.

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

Usage Guidelines4/5

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

Gives concrete identification instructions (give MMSI, or IMO which triggers a search and costs 1 extra credit) and states the free-versus-paid conditions under which results are usable. It stops short of naming explicit alternatives for historical or area queries, so no full when-not guidance.

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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