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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), yet the description still adds substantial non-obvious context: $0.02 per call over x402 on Base, a prepaid x-credit-token header for unlimited calls, 1 free call per day, and no API key. That payment/auth/rate-limit detail is exactly the kind of information an agent needs and cannot infer from structured fields.

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 resource, windows, and trend scale, then the access/cost terms, so the most important information leads. The pricing sentence is dense but each clause (cost model, prepaid header, free tier, no API key) carries distinct operational value rather than 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?

An output schema exists, so return-shape explanation is unnecessary, and the description still provides the window set and trend scale to frame the output. Purpose, required input, cost, and auth model are all covered, leaving nothing an agent needs missing for correct invocation.

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?

There is a single parameter at 100% schema description coverage, so the schema already documents it fully. The description only restates that address is required, adding no format or semantic detail beyond the schema, which is the expected baseline for a fully-covered single-param tool.

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 resource (price & volume trend) over explicit windows (1h / 6h / 24h) with a named trend scale (strong_up → strong_down). The line 'Lets agents gauge momentum, not just a single 24h number' implicitly separates it from single-value siblings like token_price, so an agent can pick it without opening any 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?

'Gauge momentum, not just a single 24h number' gives clear context for when this is the right pick versus a plain price lookup, and the required-input note removes ambiguity. It stops short of naming an alternative tool or stating exclusions, so it is strong context without full when-not guidance.

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