bart_fareGet fare between two BART stations.
| Name | Required | Description | Default |
|---|---|---|---|
| origin | Yes | Origin station code | |
| destination | Yes | Destination station code |
| Name | Required | Description | Default |
|---|---|---|---|
| fare | Yes | ||
| origin | Yes | ||
| destination | Yes |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "destination": {
+ "type": "string"
+ },
+ "fare": {
+ "anyOf": [
+ {
+ "additionalProperties": false,
+ "properties": {
+ "amount": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "name": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "name",
+ "amount"
+ ],
+ "type": "object"
+ },
+ {
+ "type": "null"
+ }
+ ]
+ },
+ "origin": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "origin",
+ "destination",
+ "fare"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is clear. The description adds no additional behavioral context, such as fare calculation assumptions or possible variations, providing minimal value beyond the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence that directly states the tool's function. There is no unnecessary detail or repetition, making it highly concise and effective.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple tool with complete schema coverage and rich annotations, the description is sufficient. It could optionally mention ticket types or fare classes, but the output schema likely covers return values, so the description remains adequate for its scope.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema fully documents both parameters with 100% coverage, so the baseline is 3. The description does not elaborate on station code formats or expected values, merely reinforcing what the schema already states.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'Get' and the resource 'fare' with the scope 'between two BART stations', which distinguishes it from sibling tools like bart_trip or bart_departures. It is specific and unambiguous.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies use for fare queries but provides no explicit guidance on when to choose this tool over alternatives such as bart_trip. There are no exclusions or prerequisites mentioned, so the usage context is only inferred.
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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