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

Beyond the readOnlyHint/openWorldHint/idempotentHint annotations, the description discloses the live official source endpoint, mandatory on-demand retrieval, the estimated_eta fallback when live data is unavailable, and an explicit prohibition against using old cached arrivals as current data. This materially shapes behavior without contradicting 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?

Two front-loaded sentences: the first states the purpose and card contents, the second details freshness and fallback behavior. Every clause carries operational weight with no 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?

With one fully documented parameter and annotations covering safety, the description supplies the remaining essential context: output contents, live-source behavior, fallback semantics, and a staleness warning. No output schema exists, but the description gives enough shape—stop fields plus arrivals—to invoke the tool correctly.

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?

Schema coverage is 100%: the stop parameter is fully described as an official code with an example and a numeric pattern. The description adds no additional parameter nuance beyond referring to a concrete stop, so baseline 3 is appropriate.

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 concrete resource—a complete Alicante bus stop card with name, coordinates, lines, and next arrivals—and a clear retrieval purpose. It does not explicitly contrast this tool with siblings such as next_departures, so it stops short of full differentiation.

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?

Usage context is implied: use it when you need a full stop card plus current arrivals, and the description instructs that arrivals must always be fetched live. However, it provides no explicit when-to-use versus alternatives or exclusions, so an agent must infer tool selection from sibling names.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.