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

Exceptional disclosure: price ($0.002 USDC on Base), free quota, exact unpaid-call behavior (x402 v2 PaymentRequired, isError, structuredContent.accepts, retry via _meta['x402/payment']), input validated before payment, and charged only on a returned answer with settlement in _meta['x402/payment-response']. Consistent with readOnlyHint/idempotentHint annotations.

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?

Front-loaded with what the tool returns, then payment mechanics; every clause carries operational weight. The nested parentheticals make it dense but not padded.

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 no output schema, the description covers what data comes back (probes plus paid test-buys), the payment/error contract, and the free path — enough to call it correctly. It stops short of describing the report's field structure or size/ordering.

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 coverage is 100% and the single 'host' parameter already has an example, so the schema does the heavy lifting. The description only restates the one-host scoping ('for one host'), adding no format or normalization detail beyond the schema.

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?

States the specific resource and scope: 'Full receipt history for one host (up to 1000 probes plus all paid test-buys)'. That scope (exhaustive history) implicitly separates it from siblings like sample and coverage, though no sibling is named explicitly.

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 free-tier note ('first 10 calls per client per UTC day are free over HTTP GET /v1/report/{host}') implies this is the paid MCP path, but there is no explicit when-to-use-this-vs-sample/coverage/preflight guidance or statement of prerequisites beyond payment.

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