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

Annotations already indicate readOnly, idempotent, and non-destructive behavior. The description adds meaningful behavior beyond annotations: the 12-week window, the weekly series, trend, volatility, and badge, and the fact that it covers any x402 operator from the Market402 index.

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?

Two sentences with no wasted words. The core behavior is front-loaded, and the use case is stated immediately after. Every part of the description earns its place.

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 single-parameter, read-only lookup tool, the description is complete: it states what is returned, the coverage window, the source index, and when the agent should call it. The absence of an output schema is mitigated by listing the return components.

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 100% and the parameter is already described as an operator domain. The description adds value by clarifying that the operator must be an x402 operator from the Market402 index, which is more specific than the schema alone.

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 clearly identifies the tool as providing a free 12-week measured score history for an x402 operator, naming the specific data series included. It is specific about the resource and scope, and its focus on operator history distinguishes it from the many service-lookup siblings.

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?

The description gives clear usage context: 'Check a seller's record before your agent pays an unfamiliar endpoint.' It does not explicitly name alternatives or state when not to use the tool, but the trigger condition is concrete enough for an agent to select it appropriately.

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