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

No annotations beyond title are provided, so the description carries the burden. It discloses that the tool is more resource-intensive and returns per-instruction distances. While it doesn't detail response structure, it adds meaningful behavioral context about cost and content beyond what annotations offer.

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 concise sentences, front-loaded with the primary purpose and immediately followed by usage guidance. No wasted words.

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 tool with 9 parameters and no output schema, the description covers the core behavior and cost trade-off. It mentions the return includes directions with distances, which is essential, though the exact response structure is not fully specified. Schema handles parameter details adequately.

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%, with every parameter having a descriptive comment. The tool description adds no additional parameter semantics beyond what the schema already provides, so the baseline of 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 clearly states the tool provides a turn-by-turn route between two places with distance for each instruction. This specific verb+resource description distinguishes it from the sibling tool routes_eta, which is explicitly mentioned.

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 explicit guidance: 'Use ETA instead when only the travel time is wanted' and explains the trade-off ('this asks the provider for more and costs more'). This clearly directs when to use this tool versus an alternative.

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