onebusaway-mcp-server

Get Real-Time Arrivals

onebusaway_get_arrivals

Read-only

Real-time arrivals and departures at a stop. Returns predicted arrival times, schedule deviation (how many seconds late/early), vehicle positions, and any active service alerts. The predicted boolean on each arrival indicates whether GPS tracking backs the estimate — predicted=false means schedule-only. Use tripId from results for follow-up onebusaway_get_trip calls. Stop IDs use agency-prefixed format: {agencyId}_{localId} (e.g. "1_75403").

Input Schema

TableJSON Schema

Name	Required	Description
`stopId`	Yes	Agency-prefixed stop ID (e.g. "1_75403" for Metro Transit stop 75403). Use onebusaway_find_stops or onebusaway_search_stops to discover IDs.
`minutesAfter`	No	Include arrivals expected within the next N minutes — an integer from 0 to 240. Defaults to 35. For a longer horizon, use onebusaway_get_schedule_for_stop.
`minutesBefore`	No	Include arrivals that departed up to this many minutes ago — an integer from 0 to 60. Defaults to 5.

Output Schema

TableJSON Schema

Name	Required	Description
`count`	No	Number of arrivals in the time window.
`error`	No	Present when the call failed. Absent on success.
`notice`	No	Guidance when no arrivals were found — widen minutesAfter, or check onebusaway_get_schedule_for_stop for scheduled service.
`stopId`	No	The queried stop ID.
`arrivals`	No	Arrivals and departures at this stop within the requested time window.
`stopName`	No	Stop name.
`situations`	No	Active service alerts at this stop — those attached to the stop itself and those referenced by its arrivals, each listed once.
`currentTime`	No	Server time as Unix milliseconds, for computing countdown timers.
`queriedStop`	No	Stop ID queried.
`windowMinutes`	No	Time window used for the arrivals query.

Schema Changelog

Changes observed during successful MCP inspections.

Changed10 schema fields changedSep 25, 2026

changedInput schema / properties / minutesAfter / description

Previous value: -"Include arrivals expected within the next N minutes. Defaults to 35."New value: +"Include arrivals expected within the next N minutes — an integer from 0 to 240. Defaults to 35. For a longer horizon, use onebusaway_get_schedule_for_stop."

addedInput schema / properties / minutesAfter / maximum
```
Added value: +240
```
addedInput schema / properties / minutesAfter / minimum
```
Added value: +0
```
changedInput schema / properties / minutesAfter / type
```
Previous value: -"number"New value: +"integer"
```

changedInput schema / properties / minutesBefore / description

Previous value: -"Include arrivals that departed up to this many minutes ago. Defaults to 5."New value: +"Include arrivals that departed up to this many minutes ago — an integer from 0 to 60. Defaults to 5."

addedInput schema / properties / minutesBefore / maximum
```
Added value: +60
```
addedInput schema / properties / minutesBefore / minimum
```
Added value: +0
```
changedInput schema / properties / minutesBefore / type
```
Previous value: -"number"New value: +"integer"
```

changedOutput schema / properties / notice / description

Previous value: -"Guidance when no arrivals were found — e.g. try expanding the time window or check for service alerts."New value: +"Guidance when no arrivals were found — widen minutesAfter, or check onebusaway_get_schedule_for_stop for scheduled service."

changedOutput schema / properties / situations / description

Previous value: -"Active service alerts referenced by arrivals at this stop."New value: +"Active service alerts at this stop — those attached to the stop itself and those referenced by its arrivals, each listed once."

Changed9 schema fields changedSep 19, 2026

removedOutput schema / properties / arrivals / items / properties / predictedArrivalTime / anyOf
```
Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]
```
addedOutput schema / properties / arrivals / items / properties / predictedArrivalTime / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / arrivals / items / properties / stopsAway / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / arrivals / items / properties / stopsAway / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedOutput schema / properties / arrivals / items / properties / vehicleId / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / arrivals / items / properties / vehicleId / type
```
Added value: +[
+  "string",
+  "null"
+]
```

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `stop_not_found`: Stop ID does not exist on this instance. `rate_limited`: API returned a rate limit response. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `stop_not_found`: Stop ID does not exist on this instance. `rate_limited`: No upstream request slot opened within the queue wait cap, or OneBusAway returned a rate limit response. Other values are possible when a failure originates below the handler."

removedOutput schema / properties / situations / items / properties / description / anyOf
```
Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]
```
addedOutput schema / properties / situations / items / properties / description / type
```
Added value: +[
+  "string",
+  "null"
+]
```

Changed6 schema fields changedAug 24, 2026

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": [
+      "stopId",
+      "stopName",
+      "currentTime",
+      "arrivals",
+      "situations",
+      "queriedStop",
+      "count",
+      "windowMinutes"
+    ]
+  },
+  {
+    "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: `stop_not_found`: Stop ID does not exist on this instance. `rate_limited`: API returned a rate limit response. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "stop_not_found",
+            "rate_limited"
+          ],
+          "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: -[
-  "stopId",
-  "stopName",
-  "currentTime",
-  "arrivals",
-  "situations",
-  "queriedStop",
-  "count",
-  "windowMinutes"
-]

Changed5 schema fields changedMay 30, 2026

addedOutput schema / properties / count

Added value: +{
+  "description": "Number of arrivals in the time window.",
+  "type": "number"
+}

addedOutput schema / properties / notice

Added value: +{
+  "description": "Guidance when no arrivals were found — e.g. try expanding the time window or check for service alerts.",
+  "type": "string"
+}

addedOutput schema / properties / queriedStop

Added value: +{
+  "description": "Stop ID queried.",
+  "type": "string"
+}

addedOutput schema / properties / windowMinutes

Added value: +{
+  "additionalProperties": false,
+  "description": "Time window used for the arrivals query.",
+  "properties": {
+    "after": {
+      "description": "Minutes after current time included.",
+      "type": "number"
+    },
+    "before": {
+      "description": "Minutes before current time included.",
+      "type": "number"
+    }
+  },
+  "required": [
+    "before",
+    "after"
+  ],
+  "type": "object"
+}

changedOutput schema / required

Previous value: -[
-  "stopId",
-  "stopName",
-  "currentTime",
-  "arrivals",
-  "situations"
-]New value: +[
+  "stopId",
+  "stopName",
+  "currentTime",
+  "arrivals",
+  "situations",
+  "queriedStop",
+  "count",
+  "windowMinutes"
+]

First observedMay 25, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Beyond the readOnlyHint, it discloses the predicted boolean semantics (predicted=false means schedule-only), what fields arrive with each result, and that service alerts are included. This materially helps the agent interpret responses.

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?

Four dense sentences with no filler; the core purpose is front-loaded and each additional sentence adds distinctive value.

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 read-only, single-required-parameter lookup with a full schema and output schema, the description covers return semantics, follow-up usage, and ID format. Nothing needed for correct invocation is missing.

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%, so the schema already documents stopId, minutesAfter, and minutesBefore with types, defaults, ranges, and examples. The description adds only a repeated stop-ID format example, not new parameter meaning.

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: real-time arrivals and departures at a stop, and enumerates the data returned. The title and first sentence align, and it is clearly distinguishable from schedule-focused siblings.

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

Usage Guidelines5/5

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

Explicitly tells the agent when to use it and when not: for real-time arrivals, and in minutesAfter it directs longer horizons to onebusaway_get_schedule_for_stop. It also routes tripId results to onebusaway_get_trip.

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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