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

No annotations are provided, so the description carries full behavioral burden. It only says 'Get public transit routes' without disclosing what the returned routes contain, whether schedules are real-time or static, or any limitations on unsupported locations or cross-border travel.

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 core action is front-loaded in a short sentence, followed by a compact list of supported countries and operators. The list is appropriately detailed and lacks filler or repetition.

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 two-string-parameter read tool without an output schema, the description omits the return format and any constraints (e.g., whether routes can be cross-country, what happens for unsupported regions). It does provide valuable operator-coverage context, but not enough to be fully complete.

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 description coverage is 100%: origin and destination are both described with concrete examples ('Barcelona Sants', 'Madrid Atocha'). The description adds context on which transportation operators are relevant, but does not meaningfully extend the parameter semantics beyond the schema.

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?

States a specific verb and resource: 'Get public transit routes between two locations.' The long list of supported countries and operators (Spain Renfe, TransMilenio, Deutsche Bahn, SJ, SBB) clearly distinguishes the tool from its unrelated siblings.

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 gives clear context: public transit routing in specific supported regions. It does not explicitly state when not to use the tool, and no transit-specific alternative is present among the sibling tools, but the supported countries/operators are sufficient guidance.

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