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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds substantial behavior they don't capture: the tool is paid (0.07 USDC on Base via x402), the calling agent's own wallet pays, the server never holds a wallet, and the payment challenge is free on the first call. This is exactly the extra non-annotation context an agent needs before invoking 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?

The core purpose is front-loaded in the first clause, which is good, but the pricing is stated twice ('0.07 USDC on Base via x402' and again '$0.07 USDC on Base, paid via x402') and the long parenthetical plus payment paragraph make it denser than necessary. Sentences are individually clear but the redundancy costs it.

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 paid archive-analysis tool with no output schema, the description conveys what the output classifies (signal ids/topics by trend status), the time window, and the full payment handshake. It does not describe the return payload shape or pagination, but the coverage of purpose and payment is largely sufficient to invoke 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 100%, with both 'days' (1-90) and 'payment_header' fully documented in the schema itself. The description restates the days range and the payment_header flow but adds no semantics beyond what the schema already provides, so the baseline 3 for high coverage applies.

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 precise analytical output: which signal ids/topics are 'stable, rising, new, or fading' across the last N archived days, and explicitly frames it as an 'archive compound' rather than a brief dump. It names one sibling (signal_history) as the alternative, but leaves the overlapping signal_delta and signal_topic_trace siblings unaddressed, so differentiation is only partial.

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?

It clearly names the alternative and the condition that selects it ('not a full brief dump — buy signal_history for that'), and gives a concrete two-step invocation flow for payment. It stops short of stating when this tool should NOT be used relative to signal_delta/signal_latest/topic_trace, so it is strong but not exhaustive.

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