onebusaway-mcp-server

List Transit Agencies

onebusaway_list_agencies

Read-only

List all transit agencies served by this OneBusAway instance. Returns agency IDs, names, contact info, timezone, and geographic coverage center. Agency IDs are needed for onebusaway_list_routes_for_agency and onebusaway_get_vehicles.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description
`count`	No	Number of transit agencies returned.
`error`	No	Present when the call failed. Absent on success.
`notice`	No	Guidance when no agencies were returned.
`agencies`	No	All agencies served by this OneBusAway instance.
`limitExceeded`	No	True if the upstream capped the agency list — some agencies were omitted. This endpoint has no pagination to retrieve them.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedSep 19, 2026

removedOutput schema / properties / agencies / items / properties / phone / anyOf

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

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

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

Previous value: -"Machine-readable failure mode."New value: +"Machine-readable failure mode. Declared by this tool: `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."

addedOutput schema / properties / error / properties / data / properties / reason / examples
```
Added value: +[
+  "rate_limited"
+]
```

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": [
+      "agencies",
+      "limitExceeded",
+      "count"
+    ]
+  },
+  {
+    "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.",
+          "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: -[
-  "agencies",
-  "limitExceeded",
-  "count"
-]

Changed2 schema fields changedJul 13, 2026

addedOutput schema / properties / limitExceeded

Added value: +{
+  "description": "True if the upstream capped the agency list — some agencies were omitted. This endpoint has no pagination to retrieve them.",
+  "type": "boolean"
+}

changedOutput schema / required

Previous value: -[
-  "agencies",
-  "count"
-]New value: +[
+  "agencies",
+  "limitExceeded",
+  "count"
+]

Changed3 schema fields changedMay 30, 2026

addedOutput schema / properties / count

Added value: +{
+  "description": "Number of transit agencies returned.",
+  "type": "number"
+}

addedOutput schema / properties / notice

Added value: +{
+  "description": "Guidance when no agencies were returned.",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "agencies"
-]New value: +[
+  "agencies",
+  "count"
+]

First observedMay 25, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already mark this as read-only, and the description adds useful scope and result details: it enumerates all agencies served by the instance and lists the specific returned fields. No hidden mutation or external-world behavior is suggested, and there is no contradiction with 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?

Three compact, front-loaded sentences: purpose, returned data, and downstream usage. Each sentence adds information without redundancy.

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 no-argument, read-only listing tool with an output schema, the description fully covers what an agent needs: what is listed, which fields are returned, and how the IDs feed into sibling tools. Nothing essential is missing.

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 zero parameters, so the description has nothing to document beyond what the empty schema shows. This matches the baseline of 4 for a no-parameter tool.

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 ('List all transit agencies served by this OneBusAway instance') and enumerates the returned fields (IDs, names, contact info, timezone, coverage center). This clearly distinguishes it from the sibling find/get/search tools.

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?

It provides a clear usage context: agency IDs from this call are needed before calling onebusaway_list_routes_for_agency and onebusaway_get_vehicles. It does not explicitly state when not to use it or mention alternatives, but the no-argument list-all purpose is sufficiently clear.

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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