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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the read-only nature and open-world assumption. The description adds the critical cost and payment requirement ($0.01 per call via x402) and the MPP endpoint, which are not in annotations. However, it does not disclose response format, rate limits, or error behavior. Given the annotations carry the safety profile, the description adds some value but not extensive behavioral context.

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 relatively concise, though it mixes payment details with the core purpose. The first sentence states the purpose, then the payment info follows. It is not overly verbose, but the payment info could be considered secondary. The structure is acceptable, though the purpose could be front-loaded more clearly.

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?

There is an output schema (though not shown), so return format may be covered there. However, the description omits details like the difference from drive_matrix, any prerequisites (e.g., valid place names), and how errors are handled. The payment requirement is covered, but other operational context is lacking. For a tool with moderate complexity and a sibling tool that is clearly related, more guidance is needed.

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 only 33%, with only the 'near' parameter having a description. The description adds minimal semantics: it says 'two named places' but does not explain that origin and destination are place names or how to format them. It doesn't clarify the 'near' parameter beyond what the schema provides. With low coverage, the description should compensate but does not, leaving the agent uncertain about parameter usage.

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 core function: 'Driving time/distance between two named places.' It names the resource (driving time/distance) and the operation (compute between origin and destination). However, it does not explicitly differentiate from the sibling drive_matrix, which likely computes a matrix of times/destinations, so the agent might not immediately know when to choose this over the matrix version.

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 no guidance on when to use this tool versus alternatives like drive_matrix. It only mentions the payment method, not the scenarios where a single route query is preferred over a matrix. There is no mention of limitations, prerequisites, or typical use cases. An agent would have to infer usage from the name and schema.

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