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

Annotations already cover readOnly, idempotent, openWorld, and non-destructive behavior. The description adds meaningful context beyond those: the data is free, spans a 12-week window, and includes weekly series, trend, volatility, and badge, which helps the agent understand the payload without contradicting annotations.

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, front-loaded with the core resource and data content, followed immediately by the usage condition. No filler or repetition.

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 simple read-only lookup with an output schema and complete annotations, the description supplies what is needed: what the tool returns, what the 12-week window means, and when to invoke it. Parameter requirements are fully documented in the schema, so no critical gap remains.

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?

The tool has one parameter with 100% schema description coverage, including an example domain. The description adds no syntax or format details beyond the schema, so the baseline of 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 resource — 12-week measured score history for an x402 operator from the Market402 index — with the key returned dimensions (weekly series, trend, volatility, badge). It does not explicitly differentiate from sibling tools such as search_x402_services, so it falls short of a 5.

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?

Provides a clear use condition: 'Check a seller's record before your agent pays an unfamiliar endpoint.' It gives context but does not name alternatives or when-not-to-use cases, so it is strong but not exhaustive.

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