fetch_comparisonCompare Aare river swimming conditions for multiple Swiss cities at once. Access water temperature, flow rates, and safety data to decide where to swim.
Fetch comparison data for cities (called from UI).
| Name | Required | Description | Default |
|---|---|---|---|
| cities | No |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v4.9.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure, but it only says 'fetch,' disclosing nothing about side effects, freshness, authorization, or what happens when cities is null. There is insufficient behavioral transparency for an agent to know the tool's operational characteristics.
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 short sentence, which is concise and front-loaded with the primary purpose. However, the parenthetical 'called from UI' adds little value for an agent and the brevity crosses into under-specification, leaving important details absent.
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?
Although the tool has only one optional parameter and an output schema exists, the description leaves major gaps: no usage guidance, no parameter semantics, and no behavioral context. Given the presence of similarly named siblings, this description is not complete enough for correct selection and invocation.
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 schema has 0% description coverage and the parameter 'cities' has no description in the schema. The tool description adds only 'for cities,' which does not explain the meaning of null, the expected array format, or the behavior when the parameter is omitted. The description only minimally compensates for the schema gap.
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 states a specific verb and resource: 'Fetch comparison data for cities.' This is clear about what the tool does. However, it does not differentiate from siblings like compare_cities or compare_cities_table, which likely overlap in purpose.
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 only usage hint is 'called from UI,' which implies an internal context but gives no guidance on when to use this tool versus compare_cities, compare_cities_table, or fetch_comparison alternatives. No exclusions, prerequisites, or alternative routing are provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.