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Get Vessel Locations

wsdot_get_vessel_locations
Read-only

Returns real-time AIS positions, speed, heading, ETA, and dock status for all active WSF vessels. Use for "where is the ferry now?", vessel tracking, or checking if a vessel is in service. Position data may lag by 30–60 seconds. Many fields are null for vessels not currently operating.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
errorNoPresent when the call failed. Absent on success.
noticeNoOptional notice when no vessel data is available. Absent on normal results.
vesselsNoAll WSF vessels with real-time position data.
totalCountNoTotal number of vessels returned.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed6 schema fields changed
    • changedInput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
    • addedInput schema / additionalProperties
      Added value: +false
    • changedOutput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
    • addedOutput schema / anyOf
      Added value: +[
      +  {
      +    "not": {
      +      "required": [
      +        "error"
      +      ]
      +    },
      +    "required": [
      +      "vessels",
      +      "totalCount"
      +    ]
      +  },
      +  {
      +    "required": [
      +      "error"
      +    ]
      +  }
      +]
    • addedOutput schema / properties / error
      Added value: +{
      +  "additionalProperties": {},
      +  "description": "Present when the call failed. Absent on success.",
      +  "properties": {
      +    "code": {
      +      "description": "JSON-RPC error code for this failure.",
      +      "maximum": 9007199254740991,
      +      "minimum": -9007199254740991,
      +      "type": "integer"
      +    },
      +    "data": {
      +      "additionalProperties": {},
      +      "properties": {
      +        "reason": {
      +          "description": "Machine-readable failure mode. Declared by this tool: `api_unavailable`: WSF Ferry API is unreachable or returns a non-2xx response after retries. `invalid_access_code`: WSF rejected the request because WSDOT_ACCESS_CODE is missing, invalid, or not registered. Other values are possible when a failure originates below the handler.",
      +          "examples": [
      +            "api_unavailable",
      +            "invalid_access_code"
      +          ],
      +          "type": "string"
      +        },
      +        "recovery": {
      +          "additionalProperties": {},
      +          "description": "Actionable next step for the caller.",
      +          "properties": {
      +            "hint": {
      +              "type": "string"
      +            }
      +          },
      +          "required": [
      +            "hint"
      +          ],
      +          "type": "object"
      +        },
      +        "retryable": {
      +          "description": "Whether retrying may succeed.",
      +          "type": "boolean"
      +        }
      +      },
      +      "type": "object"
      +    },
      +    "message": {
      +      "description": "Human-readable description of what went wrong.",
      +      "type": "string"
      +    }
      +  },
      +  "required": [
      +    "code",
      +    "message"
      +  ],
      +  "type": "object"
      +}
    • removedOutput schema / required
      Removed value: -[
      -  "vessels",
      -  "totalCount"
      -]
  2. Changed1 schema field changed
    • addedOutput schema / properties / notice
      Added value: +{
      +  "description": "Optional notice when no vessel data is available. Absent on normal results.",
      +  "type": "string"
      +}
  3. First observed

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true, so the read-only nature is known. The description adds valuable behavioral context: position data may lag by 30–60 seconds and many fields are null for non-operating vessels, which helps manage expectations about data freshness and completeness.

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?

Two sentences efficiently pack the return payload, usage guidance, and data caveats. The main functionality is front-loaded, and every sentence earns its place.

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?

With an output schema and readOnlyHint annotation, the description covers all essential aspects: what is returned, when to use it, and important caveats about data lag and nulls. No parameters means nothing else needs explaining.

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?

The tool has 0 parameters, so per the rubric the baseline is 4. The description doesn't need to explain parameters, and no additional parameter-related value is required.

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 states a specific verb ('Returns') and resource ('real-time AIS positions, speed, heading, ETA, and dock status for all active WSF vessels'), clearly distinguishing it from sibling tools like ferry schedules or border waits. It also provides concrete use cases ('where is the ferry now?').

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 explicitly says 'Use for' and lists three clear usage scenarios. It does not mention when not to use or alternatives, but since no sibling tool covers vessel location, this is sufficient context without exclusions.

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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