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

The description discloses pricing, payment mechanism via _meta["x402/payment"], the HTTP endpoint, and the 100-element limit, all of which go beyond the annotations. Annotations already declare readOnly and openWorld hints, and there is no contradiction; the description adds meaningful operational 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?

Two sentences with no filler, and each sentence adds distinct information: payment mechanics and core capability. However, the payment details are front-loaded ahead of the tool's actual purpose, and the protocol jargon like 'MPP (tempo)' is dense and unexplained.

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?

The output schema covers return values and annotations cover the safety profile, so those gaps are acceptable. What remains missing is parameter formatting guidance, clarification of the near parameter, and explicit usage differentiation from drive_time. This is workable for a prepared agent but not fully self-sufficient.

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 0%, so the description needed to explain origins, destinations, and near, but it only indirectly references origins and destinations and never explains their expected format. The combined 100-element cap is useful, but near is completely undocumented and address/coordinate semantics are absent.

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 identifies a drive-time matrix computation over origins and destinations, with an explicit 100-element cap. The contrast with the sibling drive_time tool makes clear this is the multi-pair matrix variant, though it lacks an explicit verb like 'compute' or 'calculate'.

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 is implied: a matrix for up to 100 origin-destination elements. However, the description never explicitly says when to choose this over drive_time or mentions any exclusions or alternative routing. An agent must infer the distinction from the tool names and the word 'matrix'.

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