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

The description carries substantial behavior the annotations cannot: exact per-call pricing across two chains, that unpaid calls cost nothing, that the failure mode is isError with a fresh-invoiceId PaymentRequired object, and the retry mechanism. This is consistent with the annotations (readOnlyHint=true for a read of analytics, idempotentHint=false matching the fresh invoiceId per call), so no contradiction arises, and the disclosure is unusually complete for a paid endpoint.

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-loads cost and then the tool's purpose, and every sentence carries information (pricing, question answered, metric list, payment error path, retry). Some density and redundancy with the title's pricing string keep it from being maximally tight, but no sentence is filler.

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 must describe returns, and it does so at a summary level (counts, UA families, 402-to-paid tallies, docs-first vs cold-402) rather than field-by-field. Given only two optional parameters and full annotation coverage, plus thorough payment-flow documentation, this is complete enough to invoke correctly, with the only soft spot being the vague shape of the returned data.

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%, so the schema already documents both window and payment_signature, giving a baseline of 3. The description adds only a little: it clarifies that payment_signature is an alternative channel for the same signed payload and reinforces that it should be omitted on the first call, which the schema already states.

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 names a specific resource and frames the exact question it answers ("How are clients finding and probing Agent Weather discovery files and paid routes?"), then enumerates the concrete outputs: raw first-party counts, UA families, 402-to-paid tallies, docs-first vs cold-402. That is well beyond restating the name. It falls short of 5 because it never names or excludes the closest siblings (get_x402_activity, payradar, get_pulse_facilitator), leaving the agent to infer the boundary from the metric list.

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?

Strong procedural guidance for the payment handshake: call unpaid to get the PaymentRequired object, then retry with the signed payload in _meta["x402/payment"] or the payment_signature argument. However, there is no guidance on when to choose this tool over sibling analytics tools, and no advice on which window to pick for which investigation.

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