Gangway AIS

Depth at a position

depth_at

Read-onlyIdempotent

The charted water depth at a position from EMODnet Bathymetry (European waters), or none where it has no figure. Not for navigation. Credits: 1, nothing where there is no depth. Needs a paid plan: Data API Plus, Pro or Scale, or a paid Watch plan (https://gangwayais.com/#pricing).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "lat": "<lat>",
      "lon": "<lon>"
    },
    "name": "depth_at"
  }
}

Input Schema

Name	Required	Description	Default
`lat`	Yes	Latitude in decimal degrees, north positive
`lon`	Yes	Longitude in decimal degrees, east positive

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 14, 2026

TDQS

A4.3/5.0

Behavior5/5

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

Annotations already declare read-only, idempotent, open-world, non-destructive, so the bar is lower — yet the description still adds cost (1 credit), an access-tier requirement with a pricing link, the empty-result behavior, and a suitability disclaimer. That is exactly the kind of operational context annotations cannot express.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The purpose is front-loaded and the pricing prerequisite earns its place, but the empty-result behavior is stated twice ('or none where it has no figure' and 'nothing where there is no depth'), which is redundant. The credits/plan/pricing sentence is compressed to the point of being slightly telegraphic.

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 two-parameter lookup with full schema coverage, complete annotations, and no output schema, the description supplies everything needed: what is returned, what is returned when nothing is found, geographic coverage, cost, and access tier. No material gap remains.

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 coverage is 100% and both parameters carry inline descriptions (lat/lon bounds and sign convention), so the schema does the heavy lifting. The description adds only indirect meaning via the 'European waters' coverage limit, which tells the agent which coordinate ranges are useful, but no format or precision guidance beyond the schema.

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 resource ('charted water depth at a position'), the exact data source (EMODnet Bathymetry), and the coverage boundary (European waters). It also says what the tool returns when no figure exists, so an agent knows exactly what it is asking for 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?

Provides real gating context: 'Not for navigation' excludes a misuse case, 'European waters' implies queries elsewhere will come back empty, and the paid-plan requirement is an explicit precondition. It does not name a fallback or alternative tool, which is the only missing piece.

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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