list_destinationsList every destination with a published price series, with how many days each rail was actually measured and the calendar span those measurements fall in. Historical observations only.
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Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, and the description adds meaningful behavioral context: the output is deliberately historical, limited to destinations with published price series, and includes two additional data elements (number of measured days and calendar span). No contradiction exists, and the description goes beyond the annotation by explaining what data the reader will actually see.
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 states the core action and object first, then packs the qualifying details into a compact clause. A second sentence reinforces the historical scope without redundancy. Every word earns its place, and there is no extraneous filler.
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 parameter-less list tool without an output schema, the description does a good job of explaining what will be returned: destinations with published price series, measured-day counts, and calendar spans. It is arguably complete for invocation purposes, though it does not mention ordering, pagination, or clarify the domain-specific meaning of 'rail,' which an agent might need to interpret the response.
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 tool has zero parameters, so the baseline is 4 per the rubric. The description does not need to explain parameter behavior because there are no inputs to configure; its focus on the output fields is appropriate and sufficient.
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 names a specific verb ('list') and resource ('every destination with a published price series'), then scopes the content with the measured-days and calendar-span details. The 'Historical observations only' qualifier sets it apart from the sibling tools, which focus on history comparison and prices rather than destination-level measurement coverage.
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 provides clear usage context: it returns historical measurement coverage for all destinations with a published price series. It does not explicitly name when to avoid this tool or mention alternatives like current_vs_history or price_history, but the historical-only restriction gives the agent enough situational understanding to select it correctly.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
list_destinations is clearly a discovery tool, while price_history provides the full series and current_vs_history provides a comparative summary. There is some overlap because both single-destination tools report stats, but the stated outputs are distinct enough for an agent to choose correctly.
list_destinations follows a verb_noun pattern, but price_history and current_vs_history are noun phrases with no consistent verb. The names are readable and reasonably descriptive, but the mix of conventions prevents a higher score.
Three tools is on the small side, but each covers a meaningful slice of the price-history workflow: enumerate available series, inspect a series, and get a current-vs-history summary. It is slightly sparse but not unreasonably so for a focused read-only server.
The server covers discovery and per-destination historical detail, plus the headline comparison statistic, so core read-only use cases are supported. Obvious gaps such as raw full-resolution series, cross-destination comparison, or any write/live-quote operations are absent but appear to be out of scope.