Datalastic Vessel Tracking & Maritime Intelligence

Get vessels in radius (area scan)

get_vessels_in_radius

Read-only

Scan a circular area and return all vessels currently within a given radius (nautical miles, greater than 0 and at most 50). Specify the center in exactly one way: lat+lon coordinates, a port (port_unlocode or port_uuid), or a vessel to center on (mmsi/imo/uuid). Optional filters: type, type_specific, exclude, nav_status, and include_unknown_type. Returns up to 500 vessels per page, each with its distance (nautical miles) from the center; if more remain, pass the response's 'next' token via the 'next' argument to page through them. Credits are charged per vessel found.

Input Schema

TableJSON Schema

Name	Required	Description
`imo`	No	Center the scan on a vessel, by IMO (exactly 7 digits).
`lat`	No	Center latitude (-90..90). Must be used together with lon. Provide exactly one center: lat+lon, a port, or a vessel identifier.
`lon`	No	Center longitude (-180..180). Must be used together with lat.
`mmsi`	No	Center the scan on a vessel, by MMSI (exactly 9 digits).
`next`	No	Optional: pagination token from a previous response's 'next' field, to fetch the next page (up to 500 vessels per page).
`type`	No	Optional: only include vessels of this type (e.g. Tanker, Cargo).
`uuid`	No	Center the scan on a vessel, by Datalastic vessel UUID.
`radius`	Yes	Required. Scan radius in nautical miles, greater than 0 and at most 50.
`exclude`	No	Optional: exclude vessels of this type.
`port_uuid`	No	Center the scan on a port, by Datalastic port UUID.
`nav_status`	No	Optional: filter by AIS navigational status number (e.g. 0 = under way using engine).
`port_unlocode`	No	Center the scan on a port, by UN/LOCODE (e.g. ESVLC).
`type_specific`	No	Optional: only include vessels of this specific subtype (e.g. LPG Tanker).
`include_unknown_type`	No	Optional: include vessels that have no/unknown type. Defaults to the API default when omitted.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`next`	Yes
`point`	Yes
`total`	Yes
`vessels`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 4, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Annotations already establish readOnlyHint and non-destructive behavior, and the description adds valuable behavior beyond that: radius bounds, pagination with a 'next' token for up to 500 vessels per page, exact center exclusivity, and credit charging per vessel. No contradiction exists between the description and 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 paragraph that states core behavior first, then center modes, filters, pagination, and cost. Every sentence contributes essential decision or invocation information without filler.

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?

For a 14-parameter tool, the description covers center exclusivity, radius constraints, filtering options, pagination behavior, and resource cost, while an output schema covers the response shape. No critical gaps remain for selection or invocation.

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?

All 14 parameters are described in the schema, so the baseline is 3. The description adds cross-parameter meaning not present in the schema, especially the requirement to specify the center in exactly one way and the pagination loop using the 'next' response token.

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 opens with a specific verb and resource: 'Scan a circular area and return all vessels currently within a given radius.' This clearly identifies the tool as a radius-based area scan and distinguishes it from single-vessel retrieval siblings such as get_vessel or get_vessel_info.

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?

The description gives clear context by framing the tool as an area scan with center alternatives (coordinates, port, or vessel) and optional filters. It does not explicitly name alternatives or provide when-not-to-use guidance, so it stops short of a 5.

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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