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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), and the description adds meaningful context beyond them: the data source (Coinbase's x402 marketplace), the refresh cadence (hourly index), the lookback window (last 30 days), and the measurement basis (prices "paying wallets actually accept", distinct paying wallets rather than raw calls). It does not mention rate limits or latency, so it is not exhaustive.

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?

Three sentences, all front-loaded: the resource and source first, then the report contents, then the use case. The enumeration of report outputs is dense but each item earns its place by telling the agent what it will get back.

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?

There is no output schema, so the description carries the burden of describing return values, and it does so thoroughly (price stats, distribution, top sellers, new listings, concentration metric). Combined with annotations covering the read-only safety profile and full schema documentation of the three parameters, an agent has everything needed to call it 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 all three parameters (limit, query, category) documented in the schema itself, so the baseline is 3. The description restates the category/query distinction and the 30-day window but adds no format or edge-case detail (e.g., query vs. category precedence, what happens when both are supplied).

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 scope: an hourly index of Coinbase's x402 marketplace (~38,000 pay-per-call endpoints) reporting prices and sellers. It enumerates exactly what the report contains (median/middle/top-10% prices, distribution, top sellers by distinct paying wallets, new listings, concentration), which makes it clearly distinguishable from per-vendor siblings like find_best_api or vendor_trust_profile.

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?

"Use it to price your own x402 endpoint, or to pick which paid tool to call" gives explicit when-to-use context. However, no when-not condition or named alternative is given, so it stops short of full routing guidance.

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