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

Annotations only cover readOnlyHint and openWorldHint; the description adds substantial context beyond that: the data source and update cadence, response signing, and an explicit payment requirement ($0.01 USDC per call via x402 on Base or Solana). The hijacked-listing warning explains why wallet-change data matters, which is genuine behavioral insight.

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 purpose, then change categories, then scope/parameter behavior, then signing and price. Every element is load-bearing (the wallet-hijack aside and payment terms are not filler), though the single dense paragraph could be broken up for easier scanning.

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 and only two annotations, the description supplies everything an agent needs to decide and call: data source, change taxonomy, time scope, parameter modes, payment cost, and the signing guarantee. Nothing material is missing for a read-only, pay-per-call listing-diff tool.

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 0%, so the description must carry parameter meaning, and it does: days scopes market-wide queries to 1–7 days, host switches to a single service's 30-day change log. It implies mutual exclusivity between the two modes but does not state defaults or what happens if both are supplied, leaving a small gap for an undocumented, untyped 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 a specific verb+resource (what changed in x402 service listings) and names the data provenance (daily snapshots of Coinbase's Bazaar). Enumerates the change categories (price raises/cuts, endpoint adds/drops, new/departed services, payout-wallet changes), which sharply distinguishes it from siblings like checks_service, checks_top, and crowd_changes.

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?

Explains the two operating modes and how to select them: market-wide for the last 1–7 days, or a single service's 30-day change log via host=. It also gives a when-to-use trigger ('worth checking before paying'). It stops short of naming alternative siblings for related queries, so it is clear rather than exhaustive.

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