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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description goes further by disclosing the paid x402 flow: cost ($0.07 USDC on Base), that the calling agent's own wallet pays and the server never does, and the first-call-without-payment_header challenge pattern. This is material behavioral context an agent cannot get from annotations alone.

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 the paid notice and when-to-use, but the prose is repetitive: the $0.07 cost, 'buy signal_history for that', and 'stored editions, not calendar days' each appear roughly twice, and the wallet-payment point is restated. Tighter editing would preserve all value in less space.

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, no-output-schema tool this is comprehensive: it explains cost, payment mechanics, the challenge-first call pattern, and what the returned analysis represents (continuity states across N editions). Nothing an agent needs to invoke it correctly appears to be missing.

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 both parameters are already fully documented, including the 'stored editions, not calendar days' nuance and the payment_header signing workflow. The description reinforces these but adds essentially no meaning beyond the schema. Baseline 3 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?

States a specific verb and resource — surfacing which signal ids/topics are stable, rising, new, or fading across stored editions — and names exactly which siblings it is not (signal_history, signal_topic_trace). An agent can distinguish it from siblings without opening a schema.

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?

Explicit when-to-use ('when you want to see which threads persist, rise, appear or fade across days, without paying for the full briefs') plus explicit when-not with named alternatives for both cases (signal_history for full text, signal_topic_trace for one thread's path). Nothing is left to inference.

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