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

Annotations already declare readOnlyHint and destructiveHint false. The description adds that it never performs payment or contact, reinforcing the safety, but doesn't disclose other behaviors like rate limits or data freshness. No contradiction.

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, concise and front-loaded with the key point. The qualifier 'FREE read-only' at the start is useful, and the negative guarantee is short. No fluff.

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 3 parameters at 0% coverage and no output schema, the description is insufficient. It doesn't explain what each parameter does or what the returned data looks like, so an agent would struggle to configure calls 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 description coverage is 0%, so the description must compensate. It mentions 'tiers' and 'policy invariants' which hint at the 'tier' parameter, but doesn't explain 'q' or 'budgetMicros'. The parameters remain largely unexplained, making it hard to know what to pass.

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 states it returns canonical Commerce V3, x402 rail, tiers, and policy invariants, providing a clear resource and purpose. It distinguishes itself by mentioning it is a handshake, but it doesn't explicitly differentiate from siblings like mars_commerce_quote or discover_commercial_counterparties.

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 implies it's a free read-only handshake, but it doesn't explicitly state when to use this tool versus alternatives. It mentions it never performs payment or contact, which rules out some use cases, but lacks explicit when-to-use or when-not-to-use guidance.

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