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

With no annotations, the description carries the full behavioral burden and does substantially: it discloses the cost ($0.05 in USDC on Base via x402) and the unpaid-path behavior (returns the 402 challenge). It omits error handling, rate limits, or what the evidence/basis fields look like, but the payment semantics are a meaningful disclosure.

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 the purpose front-loaded before the payment/x402 detail. The second sentence is dense and semicolon-heavy but every clause contributes useful information, so little is wasted.

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 single-parameter lookup with no output schema, the description covers purpose, return content (fee percentage, evidence, basis), and the paid/402 behavior. It is close to complete, with only minor gaps around error and response details.

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% for the single 'venue' parameter with its enum, so the schema already documents the input. The description adds no format or semantics beyond what the schema provides, making the baseline 3 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 states a specific resource and what it returns: the measured execution cost for one venue, expressed as a fee percentage with evidence and a basis. It is clear what the tool fetches, but it never distinguishes itself from the sibling list_venues or explains the relationship between them.

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?

There is no explicit when-to-use, when-not-to-use, or alternative (e.g., list_venues) guidance. The mention of payment and the 402 challenge hints at invocation mechanics but does not tell the agent under what circumstances this tool should be chosen.

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